Hyundai Excel X2 1989-1998 Fuel System

FUELSYSTEMReturn To Main Table of Contents[MPI SYSTEM]GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

MPI SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

INJECTOR AND THROTTLE BODY . . . . . . . . . . . . . . . . . . . .54

THROTTLE BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

FUEL TANK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59

FUEL LINE AND VAPOR LINE . . . . . . . . . . . . . . . . . . . . . . . .64

ENGINE CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66

[FBC SYSTEM]GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69

SERVICE ADJUSTMENT PROCEDURES . . . . . . . . . . . . . .9 3

FUEL TANK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106

FUEL LINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108

FUEL PUMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110

CARBURETOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113

ENGINE CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133

GENERAL

SPECIFICATIONS

Fuel tankCapacity

Fuel filter

TypeFuel pump

TypeDriven by

Throttle bodyThrottle position sensor (TPS)

TypeResistanceOutput voltage at curb idle

Idle speed control (ISC) servo motor

TypeResistance

Idle position switch

TypeMotor position sensor (MPS)

TypeResistance

Input sensorAir flow sensor (AFS)

TypeIntake air temperature sensor

TypeResistance

Coolant temperature sensor

TypeResistance

Oxygen sensor

TypeVehicle speed sensor

Type

45 lit. (11.9 U.S. gal., 9.9 lmp.gal.)

High pressure type

Electrical, in-tank typeElectric motor

Variable resistor type3 .5 -6 .5 KD0.48-0.52 V

Electric motor5-35 fl at 20C (68F)

Contact type within ISC servo

Variable resistor typeApprox. 4-6 Kn

Karman vortex type

Thermistor type2.33-2.97 Kn at 20C (68F)

Thermistor type2.5 Kfi at 20C (68F)0.3 Kfi at 80C (176F)

Zirconia sensor

Reed switch type

3 1 - 2

GENERAL

No. 1 cylinder TDC sensor

TypeCrankshaft angle sensor

TypeOutput actuator

Injector

TypeNumberCoil resistance

Purge control solenoid valve

TypeEGR control solenoid valve [California Only]

TypeFuel pressure regulator

Regulated pressure

Photo diode sensor

Photo diode sensor

Electromagnetic type413-16 R at 20C (68F)

ON/OFF type

Duty cycle type solenoid valve

330 kPa (3.35 kg/cm2, 48 psi)

SEALANT

Water temperature sensor assy LOCTITE 962T or equivalent

3 1 - 3

SERVICE STANDARD

Basic ignition timingCurb idle speedThrottle-position sensor (TPS) adjustment voltage

BTDC 5 2 at curb idle700 100 rpm0.48-0.52V at curb idle

TIGHTENING TORQUE Nm Kg.cm lb.ft

Delivery pipe installation screwWater temperature sensorWater temperature gauge unitOxygen sensorThrottle position sensor (TPS) installation screwFuel pressure regulator lock nutHigh pressure hose and fuel main pipe eye boltHigh pressure hose and fuel filterFuel pump assembly to fuel tankHigh pressure hose at fuel tankThrottle body to surge tankFuel tank drain plugFuel filter mounting boltAccelerator arm bracket bolts

1 0 - 1 3 100 -130 7.2-9.4

2 0 - 3 9 200 -400 1 5 - 2 9

1 0 - 1 2 100 -120 7.2-8.7

3 8 - 4 9 400 -500 2 9 - 3 6

1.5-2.5 1 5 - 2 5 1 . 1 - 2

7 - 1 1 7 0 - 1 1 0 5 - 8

2 9 - 3 9 300 -400 2 2 - 2 9

2 5 - 3 4 250 -350 1 8 - 2 5

2 - 3 2 0 - 3 0 1.5-2.2

2 9 - 3 9 300 -400 2 2 - 2 9

1 0 - 1 3 100 -130 7.2-9.4

1 5 - 2 5 150 -250 1 1 - 1 8

9 - 1 4 9 0 - 1 4 0 6 .5 -10

8 - 1 2 8 0 - 1 2 0 5.8-8.7

3 1 - 4

GENERAL

SPECIAL TOOLS

3 1 - 5

TROUBLESHOOTING

When checking and correcting engine troubles, it is importantto start with an inspection of the basic systems. If one of thefollowing conditions exists, (A) engine start failure, (B) unstableidling or (C) poor acceleration, begin by checking the followingbasic systems.

1. Power supply1) Battery2) Fusible link3) Fuse

2. Body ground3. Fuel supply

1) Fuel line2) Fuel filter3) Fuel pump

4. Ignition system1) Spark plugs2) High-tension cables3) Distributor4) Ignition coil

5. Emission control system1) PCV system2) EGR system3) Vacuum leak

6. Others1) Ignition timing2) Idle speed

Troubles with the MPI system are often caused by poorcontact of the harness connectors. It is important to checkall harness connectors and verify that they are securelyconnected.

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GENERAL

MPI TROUBLESHOOTING PROCEDURES

PROBLEM

Engine will not start

o Battery1. Connection2. Specific gravity, charging system3. Drive belt4. Voltage

o Fusible link

o Ignition switcho Starter relayo Startero Wiring

Trouble codeso Using voltmeter

[Refer to page 31-32]o Using MUT

[Refer to page 31-35]

Oil filler capo Oil dipstico Vacuum hose connectionso PCV hoseo EGR system

o High tension cableso Distributoro Ignition coil, power transistoro Spark plug

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GENERAL

o Ignition timing-adjust[Refer to page 27-5]

3 1 - 8

o Fuel line (leakage, deformation)o Fuseo Fuel pump [Refer to page 31-24]o Fuel filtero Fuel pressure regulator

o Wiring connectionso Power to ECU

1. Fusible links

2. Fuses3. MPI control relay

o Engine coolant temperaturesensor

o Intake air temperature sensor

o Injection signal circuit1. Injector wiring2. ECU

o TPSo AFS

GENERAL

PROBLEM

Rough idle or engine stalls

T r o u b l e C o d e s

[Refer to page 31--32]

o Using voltmeter

o Using MUT [Refer to page 31-35]

o Oil filler capo Oil dipstico Vacuum hose connectionso PCV hoseo EGR system

o Fuel line (leakage, deformation)o Fuseso Fuel pump [Refer to page 31-24]o Fuel filtero Fuel pressure regulator

Element-Clean or replace

Idle speed-Adjust[Refer to page 31-20]

Ignition timing-Adjust[Refer to page 27-5]

3 1 - 9

GENERAL

o Fuel pump [Refer to page 20-24]o Fuel filtero F u e l r e g u l a t o r

Injection condition

o Wiring connectionso Power to ECU

1. Fusible links2. Fuses3. MPI control relay

o Engine coolant temperaturesensor

o Intake air temperature sensoro Injection signal circuit

1. Injector wiring2. ECU

3 1 - 1 0

GENERAL

PROBLEM

Engine hesitates or accelerates poorly

o Clutch-slipo Brake-drag

o Oil filler capo Oil dipstico Hose connectionso PCV hoseo EGR system

Element-Clean or replace

Trouble codes

o Using voltmeter

[Refer to page 31-32]o Using MUT

[Refer to page 31-35]

o High tension cables

o Distributor

o Ignition coil, ignition

Ignition timing-Adjust[Refer to page 27-5]

o Fuel pump

[Refer to page 31-24]o Fuel filtero Fuel pressure regulator

3 1 - 1 1

3 1 - 1 2

GENERAL

Fuel Tank And Fuel Line

Symptom Probable cause

Engine malfunctionsdue to insufficient fuel

supply

Bent or kinked fuel pipe or hoseClogged fuel pipe or hoseClogged fuel filter of in-tank fuel filterWater in fuel filter

Dirty or rusted fuel tank interiorMalfunctioning fuel pump (Clogged filter

in the pump)

Evaporative emissioncontrol system malfunc-tions (when fuel fillercap is removed, pressureis released)

Incorrect routing of a vapor lineDisconnected vapor lineFolded, bent, cracked or clogged vapor lineFaulty fuel tank capMalfunctioning overfill limiter (Two-way

valve)

Remedy

Repair or replaceClean or replaceReplaceReplace the fuel filter or clean thefuel tank and fuel linesClean or replaceReplace

CorrectCorrectReplaceReplace

3 1 - 1 3

MPI SYSTEM

MPI SYSTEM

GENERAL INFORMATION

The basic function of the MPI (Multi-Point Injection) system isto control the air-fuel ratio, based on data from various sensors.The MPI system is composed of three basic systems: Fuel, Intakeand Electronic Control.

Fuel System

Fuel is supplied under constant pressure to the injectors by anelectric fuel pump in the fuel tank. The pressure is controlledby the pressure regulator. Based on ECU signals, the injectorsinject fuel jnto the intake manifold in the correct firing order.

Intake System

The flow rate of the intake air is measured by the AFS (Air FlowSensor) in the air cleaner. The amount of intake air during idling,warm-up and deceleration is controlled by the ISC (Idle SpeedControl) servo through the ECU.

Electronic Control System

The electronic control system is composed of sensors, whichmonitor engine conditions, and the Electronic Control Unit (ECU),which calculates the injection timing and air/fuel ratio accordingto the signals from the sensors.The sensors convert such conditions as the amount of intake air,amount of oxygen in the exhaust gas, coolant temperature,intake air temperature, engine speed, and vehicle speed intoelectrical signals, which are sent to the ECU.Analyzing these signals, the ECU determines the amount of fuelto inject and drives the injectors. The fuel injection is sequentialinjection type, in which four injectors are sequentially driven.During idling, the ISC Servo is driven according to engine loadto assure stable idling.

3 1 - 1 4

MPI SYSTEM

LOCATION OF COMPONENTS

A. Air conditioner relayB. Air flow sensorC. ISC servo (Motor position sensor)D. Throttle position sensorE. Coolant temperature sensorF. Power transistorG. Crankshaft angle sensorH. injectorI. Oxygen sensor

J. Inhibitor switchK. MPI control relayL. Diagnosis terminalM. Vehicle speed sensorN. Electronic control unitO. EGR temperature sensor (California vehicles only)P. Power steering oil pressure switchQ. Purge control solenoid valveR. EGR control solenoid valve

3 1 - 1 5

MPI SYSTEM

3 1 - 1 6

MPI SYSTEM

MPI SYSTEM

3 1 - 1 8

MPI SYSTEM

SERVICE ADJUSTMENT PROCEDURES

Idle Speed Check Procedure

CAUTIONThe improper setting (throttle valve opening) will increaseexhaust gas temperature at deceleration, reducing catalyst lifegreatly and deteriorating exhaust gas cleaning performance.It also has effect on fuel consumption and engine braking.

Checking conditions:

o Engine coolant temperature is 80 to 95C (176 to 205F).o Lights, electric cooling fan and all accessories are off.o Transaxle is in neutral [P or N range for A/T vehicles].o Steering wheel is a straight ahead position (Vehicles with

power steering).

1.

2.3.

4.

5.6.

Install the tachometer and the timing light, or connect themulti-use tester to the diagnostic connector in the fuse box.Run the engine at curb idle speed.Check the basic ignition timing and adjust if necessary.Refer to Group 27.Run the engine for more than 5 seconds at an engine speedof 2,000 to 3,000 rpm.Run the engine at idle for 2 minutes.Read the idling rpm. If the multi-use tester is used, presscode No.22 and read the idling rpm. If it is not within thespecified valve, check the idle speed control system.

Curb idle rpm . . . . . . . . . . . . . . . . . . . . . . . . . . . 700 100 rpm

Idle Speed Control (ISC) And Throttle PositionSensor (TPS) Adjustment

Adjustment conditions:o Engine coolant temperature is 80 to 95C (176 to 205F)o Lights, electric cooling fan and all accessories are off.o Transaxle is in neutral [P or N range for A/T vehicles].o Steering wheel is a straight ahead position (Vehicles with

power steering).

1. Loosen the accelerator cable.

2. Connect the multi-use tester to the diagnostic connector inthe fuse box.

3. If the multi-use tester is not used, install a tachometer anda voltmeter.

3 1 - 2 0

MPI SYSTEM

4. Turn the ignition switch to ON (do not start the engine) andleave it in that position for 15 seconds or longer; then checkto be sure that the idle speed control servo is fully retractedto the curb idle position.

NOTEWhen the ignition switch is turned to ON, the ISC plungerextends to the fast idle position opening; then, after 15seconds, it retracts to the fully close (curb idle) position.

Motor position sensor : 0.9V

5. Turn the ignition switch OFF.6. Disconnect the ISC motor connector and secure the ISC

motor at the fully retracted position.

7. In order to prevent the throttle valve from sticking, open ittwo or three times; then release it to let it click shut, andsufficiently loosen the fixed SAS.

8. Start the engine and let it run at idle speed.9. Check that the engine rpms are within the standard value.

If the multi-use tester is used, press code No. 22 and readengine rpms.

Curb idle rpm. . . . . . . . . . . . . . . . . . . . . . . . . . .700 100 rpm

10. If the engine speed is not as specified, adjust the ISCadjusting screw to obtain the standard rpm.

NOTE1. The engine speed on a new vehicle driven less than

500 Km (300 miles) may be 20 to 100 rpm lower thanspecification, but no adjustment is necessary.

2. If the engine stalls or the engine speed is low after thevehicle has been driven a distance of 500 km (300miles) or more, a deposit on the throttle valve area issuspected. Clean the throttle valve area. [Refer to page3 1 - 2 3 ]

11. Tighten the fixed SAS until the engine speed starts toincrease. Then, loosen it until the engine speed ceases todrop (touch point) and then loosen a half turn from the touchpoint.

12. Stop the engine.

3 1 - 2 1

MPI SYSTEM

13. Turn the ignition switch to ON (do not start engine) andcheck that the TPS output voltage is as specified.If the multi-use tester is used, press code No. 14 and readthe voltage.

Standard value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.48-0.52V

14. Connect a digital-type voltmeter between terminal 24 andterminal 19 of the ECU, if the multi-use tester is not used.

NOTE1. Do not disconnect the ECU connector from the ECU.2. Use an accurate digital voltmeter.

15. If it is out of specification, loosen TPS mounting screws andadjust by turning the TPS.

NOTETurning the TPS clockwise increases the output voltage.

CAUTIONTighten the screws securely after adjustment.

16. Turn the ignition switch to the OFF position.17. Adjust the accelerator cable play.

Standard valueA/T-4 . . . . . . . . . . . . . . . . . . . . . . . 3-5 mm (0.12-0.2 in.)Except above.. . . . . . . . . . . . . . . 1-2 mm (0.04-0.08 in.)

18. Connect the ISC motor connector.19. Disconnect the voltmeter, and connect the TPS connector.20. Start the engine and check to be sure-that the idle speed

is correct.21. Turn the ignition switch to OFF and disconnect the battery

terminal for 15 seconds and then re-connect. (This erasesthe data stored in memory during the ISC adjustment).

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MPI SYSTEM

Throttle Body (Throttle Valve Area) Cleaning

NOTEDisconnect the air intake hose from the throttle body, andcheck the throttle valve surface for carbon deposits, rotatingthe valve. Apply the spray cleaning solvent on the valve toremove carbon deposits.

1. Run the engine until warm.2. Remove the air intake hose from the throttle body.3. Spray cleaning solvent into the valve through the throttle

body intake port and leave it for about 5 minutes.4. Start the engine, race it several times and let it idle for about

1 minute.

NOTEIf the idle speed becomes unstable (or if the engine stalls),slightly open the throttle valve to keep the engine running.

5. Repeat steps 3 and 4.6. Attach the air intake hose.7. Disconnect the battery terminals and reconnect them more

than 10 seconds.8. Adjust the idle speed control and throttle position sensor.

Fuel Filter Replacement

1. Reduce the internal pressure of the fuel pipes and hoses bycompleting the following operations.o Disconnect the fuel pump harness connector at the rear

of the fuel tank.o Start the engine and after it stalls, turn the ignition

switch to OFF.o Disconnect the battery negative (-) terminal.o Connect the fuel pump harness connector.

2. Remove the eye bolts while holding the fuel filter nutssecurely.

CAUTIONCover with a shop towel to avoid gasoline from splashing.

3. Remove the fuel filter mounting bolts, then remove the fuelfilter from the fuel filter clamp.

4. After replacing the fuel filter, check for fuel leaks.

MPI SYSTEM

Overfill Limiter (Two-way Valve) Replacement

1. Disconnect the vapor hoses and the overfill limiter.

Fuel Sender Replacement

1. Remove the fuel filler cap to lower the fuel tanks internalpressure.

2. Disconnect the harness connector from the fuel sender.3. Remove the fuel sender unit installation screws, then

remove the fuel sender assembly from the fuel tank.

Fuel Pump Operation Check

1. Turn the ignition switch to OFF.2. Apply battery voltage to the fuel pump drive connector to

check that the pump operates.

NOTEThe fuel pump is in-tank type and its operating sound ishard to hear without removing the fuel filler cap.

3. Pinch the fuel hose to check that fuel pressure is felt.

3 1 - 2 4

MPI SYSTEM

Fuel Pressure Test

1.

2.

3.

4.5.

6.

Reduce the internal pressure of the fuel pipes and hoses bythe following procedures.1) Disconnect the fuel pump harness connector at the rear

of the fuel tank.2) Start the engine and after it stalls, turn the ignition

switch to OFF.3) Disconnect the battery negative (-) terminal.4) Connect the fuel pump harness connector.

Remove the upper, eye bolt while holding the fuel filter nutsecurely.

CAUTIONCover the hose connection with a shop towel to preventsplashing of fuel caused by residual pressure in the fuelline.

Using the fuel pressure gauge adapter (09353-24000),install the fuel-pressure gauge to the fuel filter. Tighten thebolt to the specified torque.

Tightening torqueFuel pressure gauge to fuel filter . . . . . . . . . . . . . . . . . . . . .

25-34 Nm (250-350 kg.cm, 18-25 lb.ft)

Connect the batterys negative (-) terminal.Apply battery voltage to the terminal for the pump drive andactivate the fuel pump; then, with fuel pressure applied,check that there is no fuel leakage from the pressure gaugeor connection part.

Disconnect the vacuum hose from the pressure regulator,and plug the hose end. Measure the fuel pressure at idle.

Standard value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .320-340 kPa (3.26-3.47 kg/cm2, 46-49 psi)

3 1 - 2 5

MPI SYSTEM

7. Measure the fuel pressure when the vacuum hose isconnected to the pressure regulator.

Standard value. . . . . . . . . . . . . . . . . . . . . . .Approx. 270 kPa (2.75 kg/cm2, 39 psi)

8. If the results of the measurements made in steps (6) and(7) are not within the standard value, use the table belowto determine the probable cause, and make the necessaryrepairs.

Condition

Fuel pressure too low

Fuel pressure too high

There is no difference infuel pressure when thevacuum hose is connectedand when it is not.

Probable cause

a. Clogged fuel filter.b. Fuel leakage to the return side, caused by

poor seating of the valve within the

fuel-pressure regulatorc. Low discharge pressure of the fuel pump

a. Sticking valve within the fuel-pressureregulator

b. Clogged or bent fuel return hose or pipe.

a. Clogging, or damaged vacuum hose or thenipple

b. Sticking or poor seating of the valve in thefuel-pressure regulator.

9. Stop the engine and check for a change in the fuel pressuregauge reading, which should hold for approximately 5 minutes.If the gauge indication drops, observe the rate of drop.Determine and remove the causes according to the followingtable.

Remedy

a. Replace fuel filterb. Replace fuel pressure regulator

c. Check the in-tank fuel hose forleakage or replace the fuel pump

a. Replace fuel pressure regulator

b. Repair or replace hose or pipe.

a. Repair or replace the vacuumhose or the nipple

b. Replace fuel pressure regulator

Condition

Fuel pressure drops

slowly after engine isstopped

Fuel pressure drops im-mediately after engine is

stopped

Probable cause Remedy

a. Injector leakage a. Replace injector

a. The check valve within the fuel pump is a. Replace fuel pump

open

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MPI SYSTEM

10. Reduce the fuel pressure in the fuel line.11. Disconnect the high pressure hose and remove the fuel

pressure gauge from the delivery pipe.

CAUTIONCover the hose connection with a shop towel to preventsplashing of fuel caused by residual pressure in the fuelline.

12. Install a new O-ring in the groove at the end of thehigh-pressure hose.

13. Connect the high pressure fuel hose to the delivery pipe, andtighten the screws to the specified torque.

14. Check for fuel leaks.o Apply battery voltage to the fuel pump drive terminal to

operate the fuel pump.o With pressure, check the fuel line for leaks.

EGR VALVE Control Vacuum Check

Checking ConditionEngine coolant temperature: 80-95C (176-205F)1. Disconnect the vacuum hose from the throttle body EGR

vacuum fitting and connect a hand vacuum pump to thefitting.

2. Start the engine and check to see that, after increasing theengine speed, vacuum raises proportionately to enginespeed.

NOTEIf there is a problem with the change in vacuum, it ispossible that the throttle body port may be restricted andrequire cleaning.

3 1 - 2 7

MPI SYSTEM

Purge Port Vacuum Check

Checking ConditionEngine coolant temperature: 80-95C (176-205F)1. Disconnect the vacuum hose from the throttle body purge

hose fitting and connect a vacuum pump.

2. Start the engine and check to see that, after increasing theengine speed, vacuum remains fairly constant.

NOTEIf there is no vacuum created, it is possible that thethrottle body port may be restricted and require cleaning.

3 1 - 2 8

MPI SYSTEM

MPI SYSTEM INSPECTION

If the MPI system components (sensors, ECU, injector, etc.) fail,interruption or failure to supply the proper amount of fuel forengine operating conditions will result. Therefore, the followingsituations will be encountered.1. Engine is hard to start or does not start at all.2. Unstable idle.3. Poor driveability.

If any of the above conditions are noted, first check for any ECUdiagnostic codes and then perform basic engine checks (ignitionsystem malfunction, incorrect engine adjustment, etc.), and theninspect the MPI system components with the multi-use tester(MUT) service data test.

NOTE1) Before removing or installing any part, read the diagnosis

code, then disconnect the battery negative (-) terminal.2) Before disconnecting the cable from battery terminal, turn

the ignition switch to OFF. Removal or replacement ofbattery cable during engine operation or while the ignitionswitch is ON could cause damage to the ECU.

3) The harness between the ECU and the oxygen sensor isshielded to prevent the influence of ignition noises andradio interference. When the wire is faulty, the harnessmust be replaced.

Malfunction Indicator Light

Among the self-diagnostic items, a malfunction indicator lightcomes on to notify the driver of emission control items that aremalfunctioning.However, when a signal returns to normal and the ECU sensesthat it has returned to normal, the malfunction indicator lightgoes out.Immediately after the ignition switch is turned on, themalfunction indicator light is lit for 2.5 seconds to indicated thatit is operating normally.The MIL will come ON only while the engine is running and aproblem is detected.

Items Indicated By The MIL (Malfunction Indicator Light)

o Computero Oxygen sensoro Air-flow sensoro Intake air temperature sensoro Throttle position sensor

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MPI SYSTEM

o Motor position sensoro Engine coolant temperature sensoro Crank angle sensoro No.1 cylinder top dead center sensoro Barometric pressure sensoro Injectoro Fuel pumpo EGR temperature sensor (California Vehicles Only)

SELF-DIAGNOSIS

The electronic control unit monitors the input/output signals atall times.When the ECU detects a problem for a specified time, theelectronic control unit memorizes the trouble code, and outputsa signal to the self-diagnositc output terminal.There are 14 diagnosis codes, including the normal code, thatcan be read out with a voltmeter or the multi-use tester.The diagnosis codes are memorized even if the ignition key isturned off. The trouble codes will, however, be erased when thebattery terminal or the electronic control unit harness isdisconnected.

NOTEIf a sensor connector is disconnected with the ignition switchturned on, a diagnosis code will be memorized. To erase anydiagnostic codes, disconnect the battery negative terminal (-)for 15 seconds or more, and the ECU memory will be erased.

The 13 diagnostic codes are listed below, and if more than onecode is detected, they will be indicated sequentially from thesmallest to the largest code number.

Trouble code Diagnosis item Trouble code Diagnosis item

11 Oxygen sensor

12 Air-flow sensor

13 Intake air temperature sensor

14 Throttle position sensor

15 Motor position sensor

21 Engine coolant temperature sensor

22 Crank angle sensor

23

24

25

41

42

43

No.1 cylinder top dead center sensor

Vehicle-speed reed switch

Barometric pressure sensor

Injector

Fuel pump

EGR temperature sensor (California

Vehicles Only)

3 1 - 3 0

CHECKING PROCEDURE (SELF-DIAGNOSIS)

CAUTION1) If the battery voltage is low, no trouble codes will be

stored. Be sure to check the battery voltage before startingthe test.

2) Diagnostic codes will be erased if the battery or the ECUharness is disconnected. Do not disconnect the batterybefore the diagnostic codes are read.

3) After checks and repairs are completed, disconnect the (-)ground cable for 15 seconds or more to make sure thatthe codes are erased.

Inspection Procedure (Using Mlulti-Use Tester)

1.2.

3.

4.5.6.

Turn the ignition switch OFF.Connect the harness connector of the multi-use tester to thediagnostic connector in the fuse box.Connect the power-source terminal of the multi-use testerto the cigarette lighter socket.Turn the ignition switch ON.Use the multi-use tester to check the self-diagnostic codes.After completion of the repair, turn the ignition switch OFF;then disconnect the battery negative terminal for 15 seconds.Then, check that no malfunction codes are displayed with themulti-use tester.

7. Disconnect the multi-use tester.

NOTEIf a test is to be made during cranking, the power to thecigarette lighter will be interrupted. Therefore, use theseparate battery harness for the multi-use tester.

3 1 - 3 1

MPI SYSTEM

Inspection Procedure (Using Voltmeter)

1. Connect the voltmeter to the self diagnosis connector.2. Turn on the ignition switch, and indication of electronic

control unit memory contents will immediately start. If thesystem is in normal operating condition, the pointer ofvoltmeter indicates a normal pattern. If any abnormality isin the memory, the pointer of voltmeter will deflect,indicating an abnormal item as described in Diagnosischart.After recording the abnormal item, check and repair eachpart according to the check items in Diagnosis Chart

3. When the defective parts have been repaired, disconnect thenegative terminal of the battery cable for 15 seconds ormore, reconnect it to make sure that the abnormal code hasbeen erased.

Diagnosis Chart

outputDiagnosis

Trouble codepreference Check item (Remedy)

order item Output signal pattern No. Memory

1 Electronic - - (Replace electronic control unit)controlunit

2 Oxygen 11 Retained o Harness and connectorsensor o Fuel pressure

o injectors(Replace if defective)

o Intake air leaks

o Oxygen sensor

3 Air flow 12 Retained o Harness and connectorsensor (If harness and connector

are normal, replace air flowsensor assembly)

3 1 - 3 2

MPI SYSTEM

output DiagnosisTrouble code

preference Check item (Remedy)order item Output signal pattern NO. Memory

4 Air tem- 13 Retained o Harness and connector

perature o Air temperature sensor

sensor

5 Throttle 14 Retained o Harness and connector

position o Throttle position sensor

sensor o Idle position switch

6 Motor 15 Retained o Harness and connector

position o Motor position sensor

sensor

7 Engine 21 Retained o Harness and connector

coolant o Engine coolant temperature

tempera-ture sensor

sensor

8 Crank angle 22 Retained o Harness and connector

sensor (If harness and connectorare normal, replace the

distributor assembly.)

9 No.1 cylin- 23 Retained o Harness and connector

der top (If harness and connector

dead center are normal, replace the

sensor distributor assembly.)

10 Vehicle-

speedsensor(reedswitch)

24 Retained o Harness and connectoro Vehicle-speed sensor

(reed switch)

3 1 - 3 3

MPI SYSTEM

output Diagnosis Trouble codepreference item Check item (Remedy)

order Output signal pattern No. Memory

11 Barometric 25 Retained o Harness and connector

pressure (If harness and connector

sensor are normal, replace thebarometric pressure sensor

assembly.)

12 Injector 41 Retained o Harness and connectoro Injector coil resistance

13 Fuel pump 42 Retained o Harness and connector

o Control relay

14 EGR* 43 Retained o Harness and connectoro EGR temperature sensoro EGR valveo EGR control solenoid valveo EGR valve control vacuum

15 Normal -- -

state

NOTE1. Replace the ECU only when all other possible causes for a malfunction have been explored.2. The diagnostic item marked* is applicable to the California vehicles only.

3 1 - 3 4

MPI SYSTEM

CHECKING (USING THE MULTI-USE TESTER)

1. Turn the ignition switch OFF.2. Connect the harness connector of the multi-use tester to the

diagnostic connector in the fuse box.3. Connect the power-source terminal of the multi-use tester

to the cigarette lighter socket.4. Turn the ignition switch ON.5. Use the multi-use- tester to make the system and sensor

checks.

NOTEIf the malfunction indicator light (engine-check light)illuminates while the checks are being made, check theself-diagnostic output.

6. After the repair, check again to be sure the problem has beencorrected.

7. Turn the ignition switch OFF.8. Disconnect the multi-use tester.9. Disconnect the battery negative terminal for 15 seconds or

longer. This erases the self-diagnostic code.10. Restart the engine. Check (by a driving test and other means)

that the problem has been corrected.

NOTEIf a test is to be made during cranking, the power to thecigarette lighter will be interrupted, therefore, use theseparate battery harness for the multi-use tester.

Cranking Cheek (should be performed when the engine fails to start, or before starting the engine)Item No.: Multi-use tester code number

Check points Check conditions

Battery voltageo Service datao Item No.16

o Ignition switch: ON

Testspecification

Probable cause of malfunction

11-13 v o Low battery voltageo Power not supplied to the electronic

control unit1) Check the power-supply circuit.2) Check the ignition switch.3) Check the control relay.

o Malfunction of the electronic controlunit ground circuit

3 1 - 3 5

MPI SYSTEM

Check points Check conditionsTest

specificationProbable cause of malfunction

Malfunction coderead outo Self diagnostic

Fuel pumpo Actuator testo Item No.7

o After holding for 15 seconds or Normal o Check in accordance with the diag-

longer with the ignition switch at nostic code.ON, move the ignition switch to (Note that the diagnostic code will be

LOCK and disconnect the ISC erased if there is disconnection or

servo connector. damage to the electronic control unit

o Crank for four seconds or longer. back-up power-supply circuit.)

o Ignition switch: ON o If various diagnostic codes are output,

(Check for damage or disconnec- the most frequent cause is damage or

tion of the injector or crank angle disconnection of the power-supply or

sensor circuit.) ground circuit.

Try under both Pinch off The pulsations o Voltage is not supplied to the fuelconditions: the return of the fuel flow pump.o Engine cranking hose. can be felt. 1) Check the ignition switch (IG and

o Forced fuel pump ST)activation

Listen closely The pumpto the fuel drive sound

2) Check the control relay.

tank. can be heard.3) Check the related circuits.

o Malfunction of the fuel pump.

Crank angle sensor o Engine cranking Cranking Engine speed o If the tachometer reading is 0, there

o Service data o Tachometer con- speed (rpm) (rpm) is no interruption of the ignition coil

o Item No.22 nected (check, byApprox. 200 Approx. 200

primary current.

using the tacho- 1) Check the power transistor and

meter for inter- the control circuit.

ruptions of the 2) Check the ignition coil and the coil

ignition coil power supply circuit.

primary current.) o If the multi-use testers indicated rpmis abnormal1) Malfunction of the crank angle

sensor circuit.2) Malfunction of the crank angle

sensor.3) Malfunction of the timing belt.

3 1 - 3 6

MPI SYSTEM

Check points

Injectorso Service datao Item No.41

Check conditions

o Engine cranking Listen for

operation

Enginecoolanttemperature

[C (F)]

0 (32)

20 (68)

80 (176)

Testspecification

Probable cause of malfunction

Injectors o Injector malfunction.

should be o Improper contact of the connector and

heard control relay contacts.

Injector o Malfunction of the engine coolant

activation temperature sensor.time o Malfunction of the ignition

(msec.) switch-ST.

Approx. 17

Approx. 35

Approx. 8.5

3 1 - 3 7

MPI SYSTEM

Sensor Check



Self-diagnostic

output

o Engine: idling(2 minutes or more after engine

start)

Normal o Check in accordance with the

diagnostic code.(Note that the diagnostic code willbe erased if there is disconnection

or damage of the engine controlunit back-up power-supply circuit.)

o If numerous diagnostic codes areoutput, the most frequent cause isdamage or disconnection of thepower-supply or ground circuit.

Oxygen sensoro Service datao Item No.11

o Engine warm(Make themixture lean byengine speedreduction, andrich by racing.)

Engine Voltage (mV) o If the oxygen sensor output voltagecondition is high during sudden deceleration

When sudden 200 or lower1) Check for injector leakage.

deceleration2) Check the oxygen sensor signal

from 4,000circuit.

rpmo If the oxygen sensor output voltage

is low during high engine speedWhen engine 600-1,000 1) Check the oxygen sensor andis suddenly signal circuit.rewed

o Engine warm Engine speed Voltage (mV) o If the oxygen sensor signal is

(Using the oxygen (rpm) normal, the electronic control unit

sensor signal,check the air/fuel

700 (idle) 400 or loweris regulating the air/fuel mixture

ratio normally.

mixture ratio, and 2,000 o If the oxygen sensor output voltage

also check the is low at all times, check for intake

condition of the (changes) air restriction.

electronic control o If the oxygen sensor output voltage

unit.) is high at all times, check for600-1,000 leakage of the injector.

Air-flow sensor o Engine warm Engine Frequency (Hz) o If the air-flow sensor output sud-

o Service data condition denly changes greatly, improper

o Item No.1 2700 rpm 3 0 - 5 0

contact of the air-flow sensor or

(Idle)connector is probable.

o If the output frequency of the2,000 rpm 6 3 - 8 3 air-flow sensor is unusually high or

Revving Increaseslow, check the air cleaner element.

caused byo If the output frequency of the

racingair-flow sensor is high, an increaseof engine resistance or leakage ofcompression pressure is probable.

3 1 - 3 8

MPI SYSTEM



Intake-air temper- o Ignition switch: Air temperature Temperature o Malfunction of the intake-air tem-

ature sensor ON, or engine C (F) C (F) perature or related circuit

o Service data running

o Item No.13-20 (-4) -20 (-4)

0 (32) 0 (32)

20 (68) 20 (68)

40 (104) 40 (104)

80 (176) 80 (176)

o Ignition switch: Warm by using IncreasesON a hair dryer or

other method.

Throttle-positionsensoro Service datao Item No.14

o Hold for 15 Throttle valve Voltage (mV) o Throttle position sensor misadjustedseconds orlonger with the

Idle position 480 -520o Throttle position sensor or related

circuit malfunctionignition switch Opens slowly. Becomesat ON. higher in

proportion tovalve opening

Motor positionsensoro Service datao Item No.1 5

Fully open 4,500-5,500

o Engine: Idle Engine Voltage (mV) o If the voltage is low, check whetherafter warm-up condition or not there is air intake.(The idle posi-tion switch

Idle (700 rpm) 500-1,300o If the voltage is high, the probable

cause is:must be ON.) 1) Deposits adhered to the throttle

valve2) Increased engine resistance

o If the voltage or idling speed isabnormal even though each part ofthe engine is normal, the probable

cause is:1) Improper adjustment of the idle

speed control and/or the throttleposition sensor

2) Malfunction of the motor posi-tion sensor or the related circuit.

3 1 - 3 9

MPI SYSTEM

Check points

Motor positionsensoro Sensor datao Item No.15

Check conditionsTest


The compressor Air conditioner 800-1,800 o If the engine speed does notclutch must be switch ON increase when the air conditioneractivated when (800 rpm) switch is switched from OFF to ON,the air condi- check the DC motor drive circuittioner switch is o Check the air conditioner systemswitched ON.)

Air conditioner 900-1,900 o Check the inhibitor switch and theswitch: ON signal circuitShift lever: D

range (700

rpm)

Crank signalo Service datao Item No.18

Engine coolanttemperaturesensoro Service datao Item No.21

Crank anglesensoro Service datao Item No.22

o Ignition switch: OFF o Ignition switch-ST signal circuitON check

o Ignition switch check

o Ignition switch: Engine coolant Temperature o Engine coolant temperature sensorON, or engine temperature C (F) or related circuit malfunctionrunning C (F)

-20 (-4) -20 (-4)

0 (32) 0 (32)

20 (68) 20 (68)

40 (104) 40 (104)

80 (176) 80 (176)

o Engine: idle Engine coolant Idle rpm o If the idle speed suddenly increases,(Check with the temperature a malfunction of the crank angleignition switch C (F) sensor or improper contact of theON.)

-20 (-4) 1,500-1,700connector is probable.

0 (32) 1,350-1,550

20 (68) 1,150-1,350

40 (104) 950-1,150

80 (176) 650 -850

3 1 - 4 0

MPI SYSTEM



Barometric pres- o Ignition switch: Altitude m (ft.) Pressure o Barometric pressure sensor or

sure sensor ON mm Hg related circuit malfunction.

o Service data0 (0) 760

(If the barometric pressure sensor

o Item No.25 pressure is low at high speed,600 (1,968) 710 clogging of the air cleaner element

1,200 (3,937) 660is probable.)

1,800 (5,905) 610

o Engine: Gradually close Decreases.2,000 rpm the air-intake

duct by hand.

Idle switcho Service datao Item No.26

Power-steeringswitcho Service datao Item No.27

o Ignition switch: Throttle valve ON o Idle position switch or related circuitON idling position malfunction(Checking by

Open the throt- OFFo Improper adjustment of the accel-

depressing the erator cable or the cruise controlaccelerator pedal

tle valve slightly.cable.

several times) o Misadjusted fixed SAS.

o Engine: Idle Steering OFF o Power steering oil-pressurewheel neutral switch or signal circuit malfunctionposition(wheelsstraight-aheaddirection)

Steeringwheel halfturn

ON

Air-conditionerswitcho Service datao Item No.28

o Engine: idle Air-conditioner(The air condi- switch OFFtioner compres-sor will beactivated when

Air-conditioner

the air-condi-switch ON

tioner switch isON.)

OFF

ON

o Check the air conditioner system.

Inhibitor switcho Service datao Item No.29

o Ignition switch: Shift lever: P, N o Malfunction of the inhibitor

ON P or N switch or the signal circuit.

(A/T models

only)Shift lever: D, 2, L,

o Improper adjustment of the control

D, 2, L Rcable between the shift lever and

or Rthe inhibitor switch.

3 1 - 4 1

MPI SYSTEM



EGR temperature o Engine: warm Engine Temperature o Check the EGR temperaturesensor condition C (F) sensor.[California vehicle o Check the EGR control system.

only)700 rpm 70 (158)(Idle) or less

o Check the EGR valve.

o Service data o Check the EGR control solenoid

o Item No.43 3,500 rpm 70 (158) valve.o Disconnect or more o Check the EGR control vacuum.

the vacuum

hose (yellow)stripe from theA port nippleof the throttlebody, andpinch the hoseend with yourfingers.

Injectorso Actuator testo Item No.1-4

Injectoro Service datao Item No.41

o Engine: idle Injector No. Engine o If the idling condition doesntafter warm-up

1(Cut off the

Unstable idlechange, check the cylinder.1) Check the injector operation

injectors in 2 sound.sequence dur- 2) Check the spark plug anding idle after

3high-tension cable.

engine warm- 4 3) Check the power transistor unitup; check the and control circuit.idle condition.) 4) Check injecting condition

o Engine: warmed Engine Activation o If the injector activation time is

up condition time (msec.) unusually long or short, there is a

700 rpm 2.2-2.9malfunction of the air-flow sensor,

(Idle)engine coolant temperature sensor,intake-air temperature sensor, or

2,000 rpm 1.8-2.6 barometric pressure sensor.

Rapid racing Increaseso If the injector activation time is

long, increased engine resistance orleakage of compression pressure isprobable.

Ignition advance o Engine: warmed Engine speed

(power transistor) up (rpm)o Service data o Timing light: set

o Item No.44700 (Idle)

2,000

Ignitionadvance

(BTDC)

8 - 1 2

2 6 - 3 4

o If the ignition advance and actualignition timing are different, adjustthe ignition timing.[The ignition timing may fluctuate

during idling, but this is not aproblem. The advance is greater(approx. 5) at high altitude.]

3 1 - 4 2

MPI SYSTEM

Check points

Air conditionerrelayo Service datao Item No.49

Check conditionsTest


o Engine: idle Air conditioner Air conditioner o If the air conditioner relay output isafter warm-up switch relay abnormal, check the air conditioner

OFF OFFsignal input circuit and the air

(compressorconditioner system.

clutch non-o If the activation of the air condi-

activation)tioner compressor clutch is notnormal, check the compressor

ON ON (compres- clutch and the relay circuit.sor clutchactivation)

Purge control o Ignition switch: Actuator forced Operation o Check the purge control solenoidsolenoid valve ON actuation sound is valve.o Actuator test (Engine stop) audible o Check the purge control solenoido Item No.8 valve drive circuit.

EGR control o Ignition switch: Actuator forced Operation o Check the EGR control solenoidsolenoid valve ON actuation sound is valve.[California vehicle (Engine stop) audible o Check the EGR control solenoid

only) valve drive circuit.o Actuator testo Item No.10

3 1 - 4 3

MPI SYSTEM

MPI SYSTEM COMPONENTS INSPECTION

Air Flow Sensor (AFS)

1. Connect a voltmeter between 6 and 3 of AFS connector.Terminal 6 : Sensor groundTerminal 3 : AFS output

2. Warm the engine and bring it to a normal idle.3. Measure the voltage between terminals.

Engine speed (rpm) Output voltage (V)

Idling

3,0002.7-3.2

NOTEIf the air flow sensor fails, the intake air volume cannot

be measured and as a result, normal fuel injection controlis no longer available. The vehicle can be run, however,by a preset map value.

Barometric Pressure Sensor

1. Connect a voltmeter between terminals 5 and 6 of thebarometric pressure sensor connector.Terminal 5 : Barometric sensor outputTerminal 6 : Sensor ground

2. Warm the engine and bring it to a normal idle.3. Slowly cover about half of the air cleaner air intake, checking

for a change in voltage.

Pressure

Fall

Voltage

Drop

3 1 - 4 4

MPI SYSTEM

Reference

Pressure mmHg (kPa, psi) (20, 2.9) (49, 6.9) (103, 15)150 350 760

Central voltage (V) 0.79 1.84 4.00

4. Replace the air flow sensor if necessary.

intake Air Temperature Sensor

1. Disconnect the air flow sensor connectors.2. Measure the resistance between the terminals 4 and 6.

Terminal 4 : intake air temperature outputTerminal 6 : Sensor ground

3.

4.

Temperature C (F) Resistance (KD)

0 (32) 5.4-6.6

20 (68) 2.33-2.97

80 (176) 0.31-0.43

Measure the resistance while heating the sensor using ahair drier.


Higher Smaller

If the value deviates from the standard value or theresistance remains unchanged, replace the air flow sensorassembly.

Engine Coolant Temperature Sensor

1. Remove the engine coolant temperature sensor from theintake manifold.

2. With the sensing portion of the engine coolant temperaturesensor immersed in hot water, check resistance. The sensorshould be held with its housing 3 mm (0.12 in.) away fromthe surface of the hot water.

3 1 - 4 5

MPI SYSTEM

3.


0 (32) 5.9

20 (68) 2.5

40 (104) 1.1

80 (176) 0.3

If the resistance deviates from the standard value greatly,replace the sensor.

Throttle Position Sensor (TPS)

1. Disconnect the throttle position sensor connector.2. Measure the resistance between terminals 1 and 4 of the

throttle position sensor connector.Terminal 1 : Sensor groundTerminal 4 : Sensor power

Standard value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5-6.5 Kfi

3 1 - 4 6

MPI SYSTEM

3. Connect an analog type ohmmeter between terminals 1 and3.Terminal 1 : Sensor groundTerminal 3 : Sensor output

4. Slowly open the throttle valve from the idle position to thefully open position and check that the resistance valueschange smoothly with the opening of the throttle valve.

Standard value . .. . . . . . . . . . . . . Approx 0.5 - (3.5-6.5) kfl

5. If the resistance is out of specification, or if the change isnot smooth, replace the throttle position sensor.

Tightening torqueThrottle position sensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.5-2.5 Nm (15-25 kg.cm, 1.1-1.8 lb.ft)

Idle Switch

1. Disconnect the ISC motor connector.2. Check for continuity between the terminal 3 and the body

ground.Terminal 3 : Idle Switch

Accelerator pedal Continuity

Depressed Non-conductive (MI)

Released Conductive (On)

Motor Position Sensor (MPS)

1. Connect an ohmmeter between terminals 4 and 1 of themotor position sensor connector.Terminal 1 : Sensor powerTerminal 4 : Sensor ground

2. Measure the resistance of the terminals.

Standard value . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6 kfi

3. Attach an ohmmeter between terminals 2 and 4 of the motorposition sensor connector.Terminal 2 : MPS outputTerminal 4 : Sensor ground

4. Connect a 6V battery between terminals 2 and 1 of the ISCmotor connector and check to see that resistance changessmoothly when the ISC motor is activated.

Standard value . . . . . . . . . . . . . . . . . . Approx 0.5 - (4-6) k0

3 1 - 4 8

MPI SYSTEM

5. If the standard value is not achieved, or if the change is notsmooth, replace the ISC servo assembly.

No.1 Cylinder TDC Sensor And CrankshaftAngle Sensor

1. Connect a voltmeter between terminals 1 and 2, and 1 and3.Terminal 1 : Sensor groundTerminal 2 : Crank angle signalTerminal 3 : No.1 TDC signal

2. Measure the output voltage of the terminals while crankingthe engine.

Sensor

No.1 cylinderTDC sensor

Terminal

Ground

Voltage

0.2-1.2V

(The needle fluctuates)

Crankshaftangle sensor

Ground 1.8-2.5V

3. When the voltage is abnormal, check the sensor power andground circuit, and if nothing unusual is found, disassemblethe distributor and check it.

Oxygen Sensor

NOTE

1) Before checking, warm up the engine until engine coolanttemperature reaches 80 to 95C (176 to 203F)

2) Use an accurate digital voltmeter.

1. Disconnect the oxygen sensor connector and connect avoltmeter to the oxygen sensor connector.

2. While increasing engine RPM, measure the oxygen sensoroutput voltage.

3 1 - 4 9

MPI SYSTEM

EngineOxygen sensoroutput voltage

Remarks

Increase RPM Min. 0.6V Richens air/fuel mixture

Tightening torqueOxygen sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

39-49 Nm (400-500 kg.cm, 29-36 lb.ft)

Vehicle Speed Sensor

The vehicle speed sensor uses a reed type switch. The speedsensor built in the speedometer converts the speedometer gearrevolution (vehicle speed) into pulse signals, which are sent tothe ECU.

Inhibitor Switch (For A/T)

Refer to Group 45.

Injectors

Operation CheckUsing a multi-use tester, check as described below.o Cut off the fuel injection of the injectors in sequence.o Check the operation time of the injectors.

Operation Sound Checkusing a stethoscope, check the operation sound (tick, tick) duringidle or cranking. Check that the sound is produced at shorterintervals as the engine speed increases.

NOTE1) Other injectors may produce sound as they operate even

if the injector being checked does not operate.2) Ensure that the sound from an adjacent injector is not

being transmitted along the delivery pipe to an inoperativeinjector.

3 1 - 5 0

MPI SYSTEM

Resistance Measurement Between Terminals1. Disconnect the connector for the injector.2. Measure the resistance between the terminals.

Standard value. . . . . . . . . . . . . . . . 13-16 Cl [at 20C (68F)]

3. Connect the connector for the injector.

Idle Speed control (ISC) Servo

1. Measure resistance between terminal 1 and 2 using anohmmeter.

Standard value : 5-35 Sz [at 20C (68F)]

2. Connect 6V DC to terminals 1 and 2 and check that the idlespeed control servo extends and retracts by itself.

If the idle speed control servo does not move, replace theidle speed control servo assembly.

CAUTIONApply only a 6V DC or lower voltage. Application of highervoltage could cause locking of the servo gears.

4. If the servo does not operate, replace it as an assembly.

3 1 - 5 1

MPI SYSTEM

Control Relay

CAUTIONWhen applying battery voltage directly, make sure that it isapplied to the correct terminal. Otherwise, the relay could bedamaged.

NOTEFailure of the control relay interrupts power supply to the fuelpump, injectors and ECU, resulting in start failure.

1. Check continuity between the terminals when the relay coilis energized and when it is not.

NOTEIn the following tables, the arrows indicate the directionof the current flow.Confirm circuit tester polarity before checking continuity.

o Coils L1 and L2

Condition Measuringterminals Continuity

Notenergized

1 - 4

3 - 8

2 - 8

Non-conductive (MI)

Conductive (approx. 950)

Energized

6 - 7 Conductive (approx. 35R)

1 - 4 Conductive (On)

NOTEEnergized means voltage applied across terminals 6 and7.

o Coil L3

NOTEEnergized means voltage applied across terminals 5 and7.

2. If the result is not satisfactory, replace the control relay.

3 1 - 5 2

MPI SYSTEM

Power Transistor

The power transistor is installed on the intake manifold; itfunctions to control the ignition timing by controlling the ignition

coil primary current by signals from the ECU.

1. Disconnect the power transistor connector.2. Connect a power supply of 1.5V (one dry cell) between the

power transistor and then check for continuity betweenterminals 3 and 2 under power-ON and power-OFFconditions.

NOTE1) When checking for continuity, connect the ohmmeter

to terminal 2 on the positive side and terminal 1 onthe negative side.

2) Check with an analog-type circuit tester.

3 1 - 5 3

INJECTOR AND THROTTLE BODY (MPI)

INJECTOR AND THROTTLE BODY

COMPONENTS

TORQUE : Nm (kg.cm, lb.ft)

REMOVAL

1. Release residual pressure from the fuel line to prevent fuel

from spilling.

CAUTIONCover the hose connection with a shop towel to preventfuel from leaking out due to residual pressure in the fuelline.

3 1 - 5 4


2. Remove the delivery pipe with the fuel injector and pressureregulator.

CAUTION1. Be careful not to drop any injectors when removing the

delivery pipe.2. Be aware that fuel may flow out when removing the

injector.

INSPECTION

1. Measure the resistance of the injectors between theterminals using an ohmmeter.

Resistance . . . . . . . . . . . . . . . . . . . . .13-16n [at 20C (68F)]

2. If the resistance is not within specifications, replace theinjector.

INSTALLATION

1. Install a new grommet and O-ring to the injector.2. Apply a coating of solvent, spindle oil or gasoline to the

O-ring of the injector.

3. While turning the injector to the left and right, install it onto the delivery pipe.

4. Be sure the injector turns smoothly.

NOTEIf it does not turn smoothly, the O-ring may be jammed;remove the injector and re-insert it into the delivery pipeand re-check.

3 1 - 5 5


5. When installing the delivery pipe, check to be sure that theinsulator is correctly inserted into the delivery pipesinstallation hole.

6. When connecting the fuel pressure regulator to the deliverypipe, apply light oil or fuel to the O-ring, and then insert,being careful not to damage the O-ring.

7. When connecting the high pressure fuel hose to the deliverypipe, apply fuel to the hose union, and then insert, beingcareful not to damage the O-ring.

3 1 - 5 6

THROTTLE BODY (MPI)

THROTTLE BODY

COMPONENTS


REMOVAL

CAUTIONThe throttle valve must not be removed.

3 1 - 5 7

THROTTLE BODY (MPI)

1. Remove the throttle position sensor by unscrewing the

Phillips-head screws.

NOTEExcept when necessary for replacement, the throttleposition sensor must not be removed.

2. Remove the ISC servo assembly.

NOTE

1) Except when necessary for replacement, the ISC servoassembly should not be removed.

2) The ISC servo assembly should not be disassembled.

3. Use an open-end wrench or box wrench to remove the

adjustment screw.

INSPECTION

Cleaning Throttle Body components

1. Clean all components. The following components must notbe cleaned by immersion in cleaning solvents.o Throttle position sensoro ISC servo assemblyThe insulation of these components will be damaged if theyare immersed in a cleaning solvent. They should be cleanedby using only a piece of cloth.

2. Check for restriction of the vacuum port or passage. Cleanthe vacuum passage by using compressed air.

3 1 - 5 8

FUEL TANK

COMPONENTS

REMOVAL

1. To reduce the internal pressure of the fuel lines and hoses,first start the engine and then disconnect the electrical fuelpump connector.

NOTEBe sure to reduce the fuel pressure before disconnectingthe fuel line and hose otherwise fuel will spill out.

3 1 - 5 9

FUEL TANK (MPI)

2. Disconnect the battery cable from the negative terminal ofthe battery.

3. Remove the fuel tank cap.4. Remove the drain plug and drain the fuel.

5. Disconnect the return hose and vapor hose.

6. Disconnect the fuel gauge unit connector.

3 1 - 6 0

FUEL TANK (MPI)

7. Disconnect the high pressure hose from the fuel tank.

8. Detach the fuel filler hose and leveling hose.

9. Loosen the two self-locking nuts, that hold the tank in

position and remove the two tank bands.10. Remove the fuel vapor hose and the fuel tank.

INSPECTION

1. Check the hoses and the pipes for cracks or damage.2. Check the fuel tank cap for proper operation.3. Check the fuel tank for deformation, corrosion or cracking.4. Check the inside fuel tank for dirt or foreign material.5. Check the in-tank fuel filter for damage or restriction.

3 1 - 6 1

FUEL TANK (MPI)

6. Test the two-way valve for proper operation.7. To check the two-way valve, lightly breathe into the inlet and

outlet. If air passes through after slight resistance, then thevalve is good.

INSTALLATION

1. Confirm that the pad is fully bonded to the fuel tank, andinstall the fuel tank by tightening the self-locking nuts to thetank bands until the rear end of the tank band contacts thebody.

2. Connect the leveling hose to the tank and approximately 40mm (1.6 in.) at the filler neck.

3. When connecting the filler hose, the end with the shorterstraight pipe should be connected to the tank side.

4. Connect the vapor hose and return hose.When attaching the fuel hose to the line, be sure that thehose is attached as shown in the illustration.

3 1 - 6 2

FUEL TANK (MPI)

5. To connect the high pressure hose to the fuel pump,temporarily tighten the flare nut by hand; then tighten it tothe specified torque. Be careful that the fuel hose does nottwist.

Tightening torqueHigh pressure hose flare nut . . . . . . . . . . . . . . . . . . . . . . . . .

31-41 Nm (320420 kg.mm, 23-30 lb.ft)

CAUTIONWhen tightening the flare nut, be careful not to bend ortwist the line to prevent damage to the fuel pumpconnection.

6. Connect the electrical fuel pump and fuel gauge unitconnector.

7. Tighten the drain plug to the specified torque.

Tightening torqueDrain plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-25 Nm (150-250 kg.cm, 11-18 lb.ft)

3 1 - 6 3

FUEL LINE AND VAPOR LINE (MPI)

FUEL LINE AND VAPOR LINE


REMOVAL

1. Remove the upper eye bolt while holding the fuel filter nutsecurely and remove the high pressure fuel hose.

CAUTION1) Be sure to reduce the fuel pressure before discon-

necting the fuel line and hose, otherwise fuel will spillout.

2) Cover the hose connection with a shop towel toprevent splashing of fuel that could be caused byresidual pressure in the fuel line.

2. Remove the lower eye bolt while holding the fuel filter nutassembly.

3. Remove the fuel filter mounting bolts, then remove the fuelfilter from the bracket.

4. Remove the fuel return hose and line.5. Remove the fuel vapor hose and line.

3 1 - 6 4

FUEL LINE AND VAPOR LINE (MPI)

INSPECTION

1. Check the hoses and pipes for cracking bending, deformationor restrictions.

2. Check the canister for restrictions.3. Check the fuel filter for restrictions and damage.

If a problem is found, repair or replace parts as necessary.

INSTALLATION

1. Install the fuel vapor hose and return hoses.o If the fuel line has a stepped section, connect the fuel

hose to the line securely, as shown in the illustration.o If the fuel line does not have a stepped section, connect

the fuel hose to the line securely.

2. Install the fuel filter, and tighten the fuel filter bracket.3. Insert the main line on the filter and tighten the eye bolts

while holding the fuel filter nuts.

4. Install the clips and make sure that they do not interfere withother components.

5. When installing the check valve, install it so that the valveis facing in the direction as shown in the illustration.

ENGINE CONTROL (MPI)

ENGINE CONTROL

TORQUE : Nm (kg.cm, Ib.ft)

REMOVAL

1. Remove the bushing and inner cable of the accelerator armside.

2. After disconnecting the accelerator switch connector, loosenthe bolts of the accelerator arm bracket and remove.

3 1 - 6 6

ENGINE CONTROL (MPI)

INSPECTION

1. Check the inner and outer cable for damage.2. Check the cable for smooth movement.3. Check the accelerator arm for deformation.4. Check the return spring for deterioration.5. Check the connection of the bushing to end metal fitting.6. Check the accelerator switch for proper operation.

INSTALLATION

1. When installing the return spring and accelerator arm, applymulti-purpose grease around each moving point of theaccelerator arm.

2. Apply the sealant to the bolt mounting hole, and tighten theaccelerator arm bracket.

Tightening torqueAccelerator arm bracket bolts . . . . . . . . . . . . . . . . . . . . . . . . .

8-12 Nm (80-120 kg.cm, 5.8-7.2 lb.ft)

3. Securely install the resin bushing of the accelerator cableon the end of the accelerator arm.

4. Apply multipurpose grease around the cable end.

3 1 - 6 7

GENERAL (FBC)

GENERAL INFORMATION (FBC SYSTEM)

The Feedback Carburetor (FBC) system provides a positiveair-fuel ratio control for maximum reduction of emissions. TheElectric Control Unit (ECU) receives signals from various sensorsand then modulates two solenoid valves (FBSV, SCSV) installedon the carburetor to control the air-fuel ratio.The ECU also controls the ignition timing, electric choke, throttleopener by switching on-off the solenoid valves.

FBSV : Feedback Solenoid ValveSCSV : Slowcut Solenoid ValveECU : Electric Control Unit

3 1 - 6 9

GENERAL

SPECIFICATIONS

Fuel tankCapacity

Fuel filterType [In-line filter]Type [In-tank filter]

Fuel pump

TypeDriven byFeed pressure

Carburetor

TypeIdentification mark

M / TA /T

Throttle borePrimarySecondary

Feedback solenoid valve (FBSV)

TypeCoil resistance

Slow cut solenoid valve (SCSV)

TypeCoil resistance

Throttle position sensor (TPS)

TypeRegulating voltage (When throttlevalve fully closed)Coil resistance

Bow vent valve (BVV)

TypeVacuum orifice

Mixture control valve (MCV)

TypeDash pot

TypeOperating rpm (When SAS 2 touchesfree lever)

Outer venturi dia.PrimarySecondary

Inner venturi dia.PrimarySecondary

45 lit. (11.9 U.S.gal., 9.9 Imp.gal.)

Cartridge typeOpen type

Mechanical diaphragm typeCamshaft19-25 kPa (2.76-3.63 psi) at 2,500 rpm

Down-draft, 2-barrel, feed back type

472 (For Canada), 474 (For Federal)475 (For Federal)

30 mm (1.181 in.)32 mm (1.260 in.)

Duty cycle solenoid

54-66 fl [At 20C (68F)l

Duty cycle solenoid48-60 fl [At 20C (68F)]

Variable resistor type (Rotary type)0.25V

3 .5 -6 .5 KD

Vacuum type0.3 mm (0.012 in.)

Vacuum type

Conventional type

Approx. 1,800 rpm

20 mm (0.787 in.)25 mm (0.984 in.)

9-14 mm (0.354-0.551 in.)9-12 mm (0.354-0.472 in.)

3 1 - 7 0

GENERAL (FBC)

Main jetPrimarySecondary

Main air jetPrimary - First

Second

SecondaryPilot jet

Primary

SecondaryPilot air jet

Primary - FirstSecond

SecondaryMain nozzle

Primary

SecondaryThrottle valve plate

ThicknessPrimarySecondary

Fuel closing anglePrimarySecondary

Full opening angleEnrichment jetSlow air jetAccelerating pump

Diaphragm dia.Pump jet dia.

Choke

TypeChoke valve operating angle

BimetalTemperature constantSpring constant

Choke breaker openingFirst stageSecond stage

Input sensorEngine coolant temperature sensor

TypeResistance

#83.8#145

#80#60#70

#46.3#70

#120#200#100

2.6 mm (0.102 in.)2.8 mm (0.110 in.)

1.0 mm (0.040 in.)1.5 mm (0.060 in.)

81590#50#110

24 mm (0.945 in.)0.35 mm (0.014 in.)

Automatic (Electric type)25 (When fully closed)90 (When fully opened)

1.0 deg/C60 gr.mm/deg.

1.4-1.6 mm (0.056,0.064 in.)2.9-3.1 mm (0.116-0.124 in.)

Thermistor type2.5 KR [at 20C (68F)]0.3 Ka [at 80C (176F)l

3 1 - 7 1

GENERAL (FBC)

Oxygen sensor

TypeVacuum switch

TypeOperating condition - ON

OFFVehicle speed sensorTop gear sensing switch

Output actuatorCold mixture heater

TypeSecondary air control solenoid valve

TypeResistance

Advance control solenoid valve

TypeResistance

Cold advance control solenoid valve

TypeResistance

Throttle opener control solenoid valve

TypeResistance

Zirconia sensor

Contact type switchMore than 40 kPa (5.8 psi)Less than 26 kPa (3.9 psi)Reed switch typeContact type switch

Positive Temperature Coefficient (PTC) heater

ON-OFF solenoid valve38-44fi [at 20C (68F)]

ON-OFF solenoid valve38-440 [at 20C (68F)]

ON-OFF solenoid valve

38--44fi [at 20C (68F)]

ON-OFF solenoid valve38--44fi [at 20C (68F)]

3 1 - 7 2

GENERAL (FBC)

SERVICE STANDARD

Basic ignition timing BTDC 5 1Curb idle speed 700 50 rpmThrottle opener adjusting rpm for electrical load 800 50 rpm

Throttle opener adjusting rpm for air conditioner load 900 25 rpm

TIGHTENING TORQUENm kg.cm lb.ft

Accelerator arm bracket to body 8 - 1 2 8 0 - 1 2 0 5.8-8.7Accelerator cable guide to body 3 - 5 3 0 - 5 0 2.2-3.6Carburetor attaching bolt 1 5 - 2 0 150 -200 1 1 - 1 4Engine coolant temperature sensor 2 0 - 4 0 200 -400 1 4 - 2 9Oxygen sensor 3 9 - 4 9 400 -500 2 9 - 3 6Fuel tank drain plug 7 8 - 9 8 800-1,000 5 8 - 7 2

LUBRICANT

Grease for accelerator arm pin and return spring Multipurpose grease SAE J310a, NLGI grade #3or equivalent

3 1 - 7 3

GENERAL (FBC)

SPECIAL TOOLS

3 1 - 7 4

GENERAL (FBC)

TROUBLESHOOTING

When checking and correcting engine troubles, it is importantto start with inspection of the basic systems. If you experienceone of the followings, (A) engine start failure, (B) unstable idling

or (C) poor acceleration, you should first check the followingbasic systems.

1. Power supply1) Battery2) Fusible link3) Fuse

2. Body ground3. Fuel supply

1) Fuel line2) Fuel filter3) Fuel pump

4. Ignition system1) Spark plug2) High-tension cable3) Distributor4) Ignition coil

5. Emission control system1) PCV system2) EGR system3) Vacuum leak

6. Others1) Ignition timing2) Idle speed

Troubles with the FBC system are often caused by poorcontact of harness connector. It is, therefore, important tocheck harness connector contact.

3 1 - 7 5

GENERAL (FBC)

Fuel Tank and Fuel Line

Symptom

Engine malfunctions due toinsufficient fuel supply

Evaporative emission controlmalfunctions (Pressure releasedwhen fuel tank cap is removed)

Probable cause

Bent or kinked fuel pipe or hose

Clogged fuel pipe or hose

Clogged fuel filter or in-tank fuel filter

Water in fuel filter

Dirty or rusted fuel tank interior

Malfunctioning fuel pump (Clogged filterin the pump)

Misrouted vapor lines

Disconnected vapor line piping joint

Folded, belt, cracked or clogged vapor line

Faulty fuel tank cap

Malfunctioning overfill limiter

(two-way valve)

Remedy

Repair or replace

Clean or replace

Replace

Replace the fuel filter or cleanthe fuel tank and fuel line

Clean or replace

Replace

Correct

Correct

Replace

Replace

Replace

3 1 - 7 6

GENERAL (FBC)

Carburetor and FBC System

Symptom

Engine will not startor start to hard

Rough idle or engine

stalls

Carburetor

FBC system

Carburetor

FBC system

Probable cause

Choke valve remains open-cold engine

Improper choke breaker operation

Electric choke malfunction

Needle valve sticking or clogged

Engine coolant temperature sensormalfunction

Vacuum hose disconnected or damaged

Slow-cut solenoid valve malfunction

Feedback solenoid valve malfunction

Vacuum switch malfunction-cold engine

Faulty ECU

Harness broken/short-circuited orloose connection

Choke valve malfunction

Improper fast idle-cold engine

Improper idle adjustment


Primary pilot jet clogged

Dash pot malfunction



Vacuum hose disconnected or damaged

Throttle position sensor malfunction

Engine speed sensor malfunction

Timing control system malfunction

Throttle opener control systemmalfunction

Harness broken/short-circuited orconnector not connected securely

Remedy

Clean choke bore and linkage

Check and adjust choke breaker

Check electric choke body andchoke valve operation

Repair or replace

Check by using checker (Checkcomponent and replace if faulty)

Repair or replace

Check component

Check component

Check component

Replace

Repair or replace

Clean choke bore and link

Adjust fast idle speed

Adjust idle speed

Check choke body and chokevalve operation

Clean up or replace

Adjust

Check drive signal by usingcheckerCheck component

Check by using checker (Checkcomponent and replace if faulty)

Repair or replace

Check component and adjust

Check by using checkerCheck harness for continuity

Check system. If faulty, checkcomponents

Check system. If faulty, check

components

Repair or replace

3 1 - 7 7

GENERAL (FBC)

Symptom

Engine hesitates orpoor acceleration

Engine dieseling(runs after ignitionswitch is turned off)

Carburetor

FBC system

Carburetor

FBC system

Poor fuel mileage Carburetor

Probable cause

Acceleration pump malfunction

Choke valve remains open-cold engine

Choke valve remains closed-hot engine

Main jet clogged

Enrichment jet clogged

Secondary valve operation abnormal


Vacuum switch malfunction





Cold mixture heater relay control systemmalfunction-cold engine

Harness broken/short-circuited orconnector not connected properly

Air conditioner power relay controlsystem malfunction

Engine idle speed too high


Choke valve operation abnormal

Engine idle speed too high


Enrichment valve kept open

Remedy

Clean pump discharge. rate

Clean choke bore and linkCheck choke valve operation

Clean choke bore and linkCheck choke valve operation

Clean up

Clean up

Check valve operation

Check drive signal by usingcheckerCheck component

Check with checker (Replaceif faulty)

Check system. If faulty, checkcomponents

Check by using checker (Checkcomponents and replace if faulty)


Check by using checkerCheck harnesses for continuity


components

Repair or replace

Check system

Adjust idle speed

Check component

Check valve operation

Adjust idle speed

Check choke body and valve

operation

Repair or replace

3 1 - 7 8

GENERAL (FBC)

Symptom

Poor fuel mileage FBC system

Probable cause


Oxygen sensor malfunction






Harness broken/short-circuited or

connector not connected securely

Remedy

Check by using checker(Check component and replace

if faulty)

Check by using checker(Check component and replace

if faulty)


components

Check drive signal by using

checkerCheck component

Check drive signal by usingcheckerCheck components


Check by using checkerCheck harness for continuity

Repair or replace

3 1 - 7 9

GENERAL (FBC)

FBC System Component

1. Electric Control Unit (ECU)

Based on the information- from various sensors, the ECU

determines (computes) ideal setting for varying operating

conditions and drives the output actuators to control the

air-fuel ratio.

The ECU consists of an 8-bit microprocessor, random access

memory (RAM), read only memory (ROM) and input/output

(l/O) interface.

3 1 - 8 0

GENERAL (FBC)

2. Engine Coolant Temperature SensorThe engine coolant temperature sensor is installed in theengine coolant passage of the intake manifold. This coolantsensor is a thermistor. The ECU determines enginetemperature by the sensor output voltage and utilize it toprovide optimum fuel enrichment when the engine is cold.

3. Throttle Position Sensor (TPS)The TPS is a rotary type variable resistor that rotates togetherwith the carburetor throttle shaft to sense the throttle valveangle. As the throttle shaft rotates, the TPS output voltagechanges and the ECU detects the throttle valve openingbased on the change of the voltage.Using the TPS output signal, engine speed signal and othersignals, the ECU maintains the optimum air-fuel ratio.

4. Engine Speed SensorThe ignition coil negative terminal voltage makes suddenincrease twice per crankshaft revolution synchronously withignition timing.By sensing this ignition coil negative terminal voltage changeand measuring the time between peak voltages, the ECUcomputes the engine speed, judges the engine operatingmode and controls the air-fuel ratio and ignition timing.

GENERAL (FBC)

5. Oxygen Sensor1) The oxygen sensor installed on the exhaust manifold

makes use of the principles of solid electrolyte oxygenconcentration cell. The oxygen concentration cell ischaracterized by sharp change of the output voltage inthe vicinity of the stoichiometric air-fuel ratio.

2) Using such characteristics, the oxygen sensor senses theoxygen concentration in the exhaust gas and feeds it tothe ECU. The ECU then judges if the air-fuel ratio isricher or leaner as compared to the stoichiometric ratioand provides feedback control to adjust the air-fuel ratioto the stoichiometric ratio where the emission purifi-cation rate of the three way catalytic converter is theoptimum.

6. Vacuum SwitchThe vacuum switch is a contact type switch that is operatedby intake manifold vacuum. When the throttle valve closes,the intake manifold vacuum acts on the vacuum switch toclose its contact.By this action, the voltage on the ECU side is grounded andthe ECU senses that the throttle valve opening is near idle.

3 1 - 8 2

GENERAL (FBC)

7. Feedback Solenoid Valve (FBSV)The FBSV is installed in the carburetor float chamber cover.The ECU controls the air-fuel ratio by controlling the dutycycle of the FBSV.The higher is the duty ratio, the leaner becomes the air-fuelratio.

NOTEThe duty cycle control means control of the solenoid valveenergization rate by changing the ON time ratio T2/T1(called duty ratio) of 10 Hz pulse.

8. Slow Cut Solenoid Valve (SCSV)The SCSV is located in the carburetor float chamber cover.The ECU controls the carburetor slow system fuel flow bycontrolling the duty cycle of the SCSV.

3 1 - 8 3

GENERAL (FBC)

FBC System Operation

1. The air-fuel ratio control is maintained by the ECU in oneof two operating modes.1) Closed loop control (Feedback control)

After engine warm-up, the air-fuel ratio control is madeby the feedback control based on the oxygen sensorsignal.The oxygen sensor output voltage changes sharply at thestoichiometric ratio. The control unit senses this oxygensensor signal and provides feedback control to the FBSVmaintaining the stoichiometric ratio that will give thebest purification rate of the 3-catalyst converter may beaccurately kept. In this state, the SCSV is kept wide open(100% duty).

2) Open loop control (No feedback control)During engine start, warm-up operation, high loadoperation and deceleration, the air-fuel ratio is inopen-loop. The ECU controlled based on map values*established previously for engine speed, throttle valveopening angle and engine coolant temperature, toimprove startability and driveability.During deceleration, the SCSV limits fuel flow for betterfuel economy and for prevention of overheating of thecatalysts.* Map value is a value previously established and

stored in ROM in ECU.

2. When the FBSV is energized, the main fuel jet is closed toleaving the primary main jet passage as the only fuelpassage.This reduces the amount of fuel, resulting in leaner air-fuelmixture.

3. When the FBSV is de-energized, the main fuel jet is openedto provide two fuel passages including the primary main jetpassage. Since this will increase the amount of fuel, richerair-fuel mixture is obtained.With the ON-OFF operation of SCSV, the slow fuel passageis opened and closed.The air-fuel ratio at deceleration is controlled in this manner.

3 1 - 8 4

GENERAL (FBC)

Distributor Advance Control System(Ignition Timing Control System)

The distributor vacuum advance is a dual diaphragm type havingmain vacuum chamber and sub-vacuum chamber. To control theignition timing, the ECU energizes the solenoid valves in therespective vacuum circuits of main vacuum chamber andsubvacuum chamber.

1. Main Vacuum Timing Control1) When the engine speed is near the idle speed (1,200 rpm

or less), the ECU energizes the distributor advancecontrol solenoid valve. By this action the carburetor Dport vacuum is introduced to the main vacuum chamberwhich resets the ignition timing.

NOTEThe D port vacuum is zero when the throttle valve isat idle position, and increases with the valve openingangle.

3 1 - 8 5

GENERAL (FBC)

2. Sub-vacuum Timing Control

2) When the engine speed increases to 1,200 rpm the ECUturns off the distributor advance control solenoid valve.Intake manifold vacuum is routed to the main vacuumchamber increasing ignition advance.

When the engine starts to warm up [engine coolanttemperatures: below 80C (176F), the solenoids areenergized, allowing D port vacuum to reach mainvacuum chamber.

o Control at low altitude [approx. 1,200 m (3,900 ft.) orlower]1) When the engine coolant temperature is low [50C

(122F) or lower], the ECU energizes the distributor coldadvance control solenoid valve. By this action, the intakemanifold vacuum no longer leaks to atmosphere andinstead is introduced to the sub-vacuum chamber. As aresult, the timing advanced by the main vacuum advanceis additionally advanced by a fixed angle (5C in crank

angle).2) During warm-up operation or when the engine coolant

temperature is- high [over 50C (122F)], the ECUde-energizes the distributor cold advance controlsolenoid valve circuit. As a result, the intake manifoldvacuum leaks to atmosphere, which prevents timingadvance.

o Control at high altitude [approx, 1,200 m (3,900 ft.) or over)At high altitude, the HAC is closed and hence the intakemanifold vacuum does not leak to atmosphere from the HAC.Independently of the distributor cold advance control solenoidvalve, the intake manifold vacuum acts on the sub-vacuumchamber, causing the timing to advance by a fixed angle (5in crank angle). [For Federal]

3 1 - 8 6

GENERAL (FBC)

Throttle Opener System (For power steering,electrical load)

If the power steering oil pressure switch is turned on by highpump pressure the throttle opener control solenoid valve isenergized to introduce intake manifold vacuum to the throttleopener. The throttle valve opens slightly, preventing enginespeed drop caused by power steering load.

When the engine speed drops below the set speed (1,200 rpm),the ECU keeps the power transistor on. When the electrical loadswitch is turned on for lighting etc., the throttle opener controlsolenoid valve is energized, allowing intake manifold vacuum tothe throttle opener to open the throttle valve slightly, preventingengine speed drop caused by electrical load.

3 1 - 8 7

GENERAL (FBC)

Throttle Opener Switch (For A/C)

When the engine speed is below the set speed (1,200 rpm), theECU keeps the power transistor on. When the air conditionerrelay is turned on the throttle opener control solenoid valve isenergized to introduce intake manifold vacuum to the throttleopener. The throttle valve opens slightly preventing enginespeed drop caused by air conditioner load.

Air Conditioner Power Relay Control System (For A/T)

When the throttle valve opening increases (over 74) duringacceleration etc., the ECU turns off the air conditioning powerrelay for about 5 seconds. As a result, even if the air conditionerswitch it is, the air compressor is not driven and hence theengine load is reduced, improving acceleration performance.

3 1 - 8 8

GENERAL (FBC)

Cold Mixture Heater (CMH) Relay ControlSystem

The cold mixture heater is a Positive Temperature Coefficient(PTC) heater installed between the carburetor and intakemanifold.When the engine coolant temperature is below 60C (140F), theECU energizes the cold mixture heater relay. The closed relaysupplies voltage to the cold mixture heater. The cool air-fuelmixture is heated and atomized by the heater before it reachesthe combustion chamber for improved combustion.

3 1 - 8 9

GENERAL (FBC)

Electric Auto Choke System

In the carburetor electric choke system, a bimetal choke springis heated by an electric heater (PTC heater*).

As the bimetal spring is heated by the heater after start-up, thebimetal opens the choke valve gradually by thermal expansionand pushes down the stopper lever.

The lower the temperature when the engine is started, thetighter the bimetal closes the choke valve, thus improving at coldweather starting.

*PTC heater : Positive Temperature Coefficient heater

3 1 - 9 0

GENERAL (FBC)

1. Choke Valve and Fast Idle Cam Operation1) Before starting the engine, the throttle valve is in normal

idle opening state.

2) Before starting the engine, depress the accelerator pedalto the floor, and the fast idle cam will turn clockwise.Release the accelerator pedal, and the lever will ride onthe fast idle cam and the throttle valve will open.

3) When the engine starts, the intake manifold vacuum isapplied to the choke breaker to slightly open the chokevalve, preventing a rich air-fuel mixture.

4) Shortly after starting of engine, the bimetal is heated bythe heater and expands to open the choke valve graduallyand push down the stopper lever.At this time, the engine speed increases gradually.

5) Depress the accelerator pedal, and the fast idle cam willturn counterclockwise. Release the accelerator pedal andthe lever will ride on the lower step of fast idle cam andthe throttle valve will close slightly, decreasing theengine speed. After warming up the engine for a while,depress the accelerator pedal and the throttle valve willbe further closed.By repeating this procedure, the fast idle cam is releasedand the throttle valve comes to have a normal idleopening.

3 1 - 9 1

GENERAL (FBC)

2. Operation of Choke OpenerIf the engine has been started with the throttle valve leveron the highest fast idle cam step then the engine speed willincrease with the engine coolant temperature. This resultsin the engine overrun. In order to prevent such overrun, thechoke opener is provided.

1) When the thermo valve closes as the engine coolanttemperature rises [65C (149F)], the intake manifoldvacuum acts on the fast idle breaker.

2) The fast idle breaker forces the fast idle cam tocounterclockwise so that the lever will rest on the lowestdetent of cam, closing the throttle valve to decrease theengine speed.

3. Electric Auto Choke RelayThe electric choke relay is normally closed (ON) and it openswhen its coil is energized.

During engine cranking or for approx. 80 seconds at anengine coolant temperature of -10 to 18C (-14 to 64F),the ECU energizes the electric choke relay coil. This preventsheating of the electric choke heater, until the engine hasstarted.

3 1 - 9 2

SERVICE ADJUSTMENT PROCEDURES (FBC)

SERVICE ADJUSTMENT PROCEDURES

FBC SYSTEM

Inspection

If FBC system components (sensors, carburetor control unit--computer, solenoid, etc.) fail, one of the following situations maybe encountered.1. Engine is hard to start or does not start at all.2. Unstable idle.3. Poor driveability.

If any of above conditions is noted, first perform basic enginechecks (ignition system malfunctions, incorrect engineadjustment, etc.). The FBC system can be checked by use ofFBC checker and FBC harness connector. Inspectionprocedure is as follows.

CAUTION1) Before battery terminals are disconnected, make sure

that ignition switch is OFF. If battery terminals aredisconnected while engine is running or when ignitionswitc

Hyundai Excel X2 1989-1998 Fuel System

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