Troubleshooting

TROUBLESHOOTING HINTS

1. Engine troubles are usually not caused by the EFI system When troubleshooting, always first check the condition cl the other systems.

(a) Electronic source

• Fusible links

(b) Body ground

(c) Fuel supply

(d) Ignition system

• High-tension cord

• Distributor

• Igniter and ignition coil

(e) Air intake system

(f) Emission control system

(g) Others

• Ignition timing (ESA system)

2. The most frequent cause of problems is simply a bad contact in wiring connectors. So always make sure that connections are secure.

When inspecting the connector, pay particular attention to the following points:

(a) Check to see that the terminals are not bent.

(b) Check to see that the connector is pushed in completely and locked.

(c) Check to see that there is no signal change when the connector is slightly tapped or wiggled.

3. Sufficiently troubleshoot for other causes before replacing the computer. The computer is of high quality and it is expensive.

4. Use volt/ohmmeter with high-impedance (10kQ/V minimum).

TROUBLESHOOTING PROCEDURES SYMPTOM - DIFFICULT TO START OR NO START (ENGINE WILL NOT CRANK OR CRANKS SLOWLY)

SYMPTOM - DIFFICULT TO START OR NO START (CRANKS OK)

CHECK DIAGNOSIS SYSTEM

Diagnostic code(s) (See page FI-25)

Check for output of diagnostic code. (See page FI-22)

Malfunction code(s)

Normal code

DOES ENGINE START WITH

ISC system

ACCELERATOR PEDAL DEPRESSED?

(2) Wiring connection KB ISC valve ECUH

NO

CHECK FOR VACUUM LEAKS IN AIR

2. Oil level gauge

3. Hose connections

4. PCV hoses

5. EGR system - EGR valve stays open

INTAKE LINE

BAD

OK

CHECK IGNITION SPARK

1. Plug wires

t. Unplug connectors of injector resistor and start injector time switch. 2. Check by holding spark plug wire 8 — 10 mm (0.31 - 0.39 in.) away from engine block while engine is cranking. A strong spark should be noted.

3. Distributor

4. Ignition coil, igniter

OK

CHECK IGNITION TIMING

Adjust ignition timing. (See page IG-9)

1. Short both terminals of the check connector.

2. Check ignition timing, STD: 10° BTDC

(w/short terminals of the check connector)

NO

OK

CHECK FUEL SUPPLY TO INJECTOR

1. Fuel line — leakage — deformation

1. Fuel in tank bad

2. Fuel pressure in fuel line

(1) Short fuel pump check terminals.

(2) Fuel pressure at fuel hose of fuel filter can be felt.

(See page FI-45)

3. Circuit opening relay (See page FI-69)

5. Fuel filter

6. Fuel pressure regulator (See page FI-52)

OK

CHECK FUEL PUMP SWITCH IN AIR

Air flow meter (See page FI-58)

FLOW METER

Check continuity between terminals Fc and E while measuring plate of air flow meter is open.

BAD

¡

OK CONTINUED ON PAGE FM2

OK CONTINUED FROM PAGE FI-11

CHECK SPARK PLUGS

Correct insulation resistance:

10 Mil or more

Precaution: Never attempt to adjust gap on used platinum tipped spark plug.

Check compression pressure if necessary. (See page EM-6)

CHECK EFI ELECTRONIC CIRCUIT USING VOLT/OHMMETER

1. Spark plug

2. Compression pressure

Limit: 9.0 kg/cm1 (128 psi. 883 kPal at 250 rpm

1. Injector(s) — shorted or leaking

2. Injector wiring(s) between resistor and ECU shorted

3. Cold start injector — leakage (See page FI-49)

4. Start injector time switch (See page FI-71)

1. Wiring connection

2. Power to ECU

(1) Fusible link

3. Air flow meter

4. Water temp, sensor

5. Injection signal circuit

(1) Injector wiring

(2) Resistor (31 ECU

SYMPTOM - ENGINE OFTEN STALLS

Toyota Supra Injector Wiring

CHECK EFI ELECTRONIC CIRCUIT USING VOLT/OHMMETER

Wiring connection Power to ECU

(1) Fusible link

Water temp, sensor Injection signal circuit

(1) Injector wiring

(2) Resistor

SYMPTOM - ENGINE SOMETIMES STALLS

Normal code

CHECK AIR FLOW METER

(See page FI-58)

Air flow meter

BAD

CHECK WIRING CONNECTORS AND

1. Connector

RELAYS

BAD

2. No.1 and No. 2 main relay

Check that there is a signal change when

(See page FI-68)

the connector or relay is slightly tapped

3. Circuit opening relay (See page FI-69)

or wiggled.

SYMPTOM - ROUGH IDLING AND/OR MISSING

OK CONTINUED ON PAGE FM6

JoK CONTINUED FROM PAGE FI-15

SYMPTOM - HIGH ENGINE IDLE SPEED (NO DROP)

Steckbrief Waldkaninchen

SYMPTOM - ENGINE BACKFIRES-Lean Fuel Mixture

CHECK DIAGNOSIS SYSTEM

Check for output of diagnostic code. (See page FI-22)

Diagnostic code(s) «See page FI-25)

Malfunction code(s)

Normal code

CHECK FOR VACUUM LEAKS IN AIR

2. Oil level gauge

3. Hose connections

4. PCV hoses

5. EGR system - EGR valve stays open

INTAKE LINE

BAD

OK

CHECK IGNITION TIMING

1. Short both terminals of the check connector.

2. Check ignition timing. STD: 10° BTDC

(w/short terminals of the check connector)

Ignition system (See page IG-2)

BAD

OK

CHECK COLD START INJECTOR

(See page FI-49)

1. Cold start injector

2. Start injector time switch (See page FI-71)

BAD

OK

CHECK FUEL PRESSURE

2. Fuel filter

3. Fuel pressure regulator (See page FI-52)

(See page FI-45)

BAD

OK

CHECK INJECTORS

(See page FI-53)

Injectors - clogged

BAD

OK

CHECK EFI ELECTRONIC CIRCUIT USING VOLT/OHMMETER

2. Power to ECU

(1) Fusible link

3. Air flow meter

4. Water temp, sensor

5. Air temp, sensor

6. Throttle position sensor

7. Injection signal circuit

(1) Injection wirings

(2) Resistor

(4) Fuel cut signal

8. Oxygen sensor

BAD

SYMPTOM - MUFFLER EXPLOSION (AFTER FIRE)

-Rich Fuel Mixture-Misfire

CHECK DIAGNOSIS SYSTEM

Check for output of diagnostic code. (See page FI-22)

Diagnostic code(s) (See page FI-25)

Malfunction code(s)

Normal code

CHECK IGNITION TIMING

Ignition system (See page IG-2)

1. Short both terminals of the check connector.

2. Check ignition timing. STD: 10° BTDC

(w/short terminals of the check connector)

NO

OK

CHECK COLD START INJECTOR

(See page FI-49)

1. Cold start injector

2. Start injector time switch (See page FI-71)

BAD

OK

Injectors - leakage

CHECK INJECTORS

BAD

OK

CHECK SPARK PLUGS Max. allowable gap: 1.4 mm (0.055 in.) Precaution: Never attempt to adjust gap on used platinum tipped spark plug.

Check compression pressure if necessary. (See page EM 6)

2. Compression pressure

Limit: 9.0 kg/cm2 (128 psi, 883 kPa) at 250 rpm

NO

CHECK EFI ELECTRONIC CIRCUIT USING VOLT/OHMMETER

1. Throttle position sensor

2. Injection signal

(1) Injector wiring

(2) Resistor

3. Oxygen sensor

BAD

SYMPTOM - ENGINE HESITATES AND/OR POOR ACCELERATION

CHECK FOR VACUUM LEAKS IN AIR

2. Oil level gauge

3. Hose connections

4. PCV hoses

5. EGR system - EGR valve stays open

INTAKE LINE

BAD

OK

CHECK AIR FILTER ELEMENT

Clean or replace

BAD

OK

CHECK DIAGNOSIS SYSTEM

Check for output of diagnostic code. (See page FI-22)

Diagnostic code(s) (See page FI-25)

Malfunction code(s)

Normal code

CHECK IGNITION SPARK

1. Plug wires

1. Unplug connectors of injector resistor and start injection time switch.

2. Check by holding spark plug wire 8—10 mm (0.31 - 0.39 in.) away from engine block while engine cranking. A strong spark should be noted.

m

3. Distributor

4. Ignition coil, igniter

OK

1. Short both terminals of the check connector.

2. Check ignition timing. STD: 10° BTDC

{w/short terminals of the check connector)

OK CONTINUED ON PAGE FI-21

OK CONTINUED FROM PAGE FI-20

CHECK FUEL PRESSURE

(See page Fl 45)

2. Fuel filter

3. Fuel pressure regulator (See page FI-52)

BAD

OK

CHECK INJECTORS

(See page FI-53)

Injection condition

BAD

OK

CHECK SPARK PLUGS Max. allowable gap: 1.4 mm (0.055 in.) Precaution: Never attempt to adjust gap on used platinum tipped spark plug.

Check compression pressure il necessary. ¡See page EM-6I

2. Compression pressure

Limit: 9.0 kg/cm2 (128 psi, 883 kPal at 250 rpm

NO

OK

CHECK EFI ELECTRONIC CIRCUIT

USING VOLT/OHMMETER

2. Power to ECU

(1) Fusible link

3. Air flow meter

4. Water temp, sensor

5. Air temp, sensor

6. Throttle position sensor

7. Injection signal circuit

(1) Injector wirings

(2) Resistor

(3) ECU

BAD

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