Engine Controls - Tests W/o Codes: Other Toyota Supra A80

Engine Fails To Crank

1. Check battery, cables, charging system and fusible links.
2. Check ignition switch.
3. Check starter and wiring connections.
4. Check clutch switch (M/T) or park/neutral switch (A/T).
5. Check starter relay (if equipped).
6. Check theft deterrent system (if equipped).

Engine Cranks But Fails To Start

1. Ensure proper spark exists from ignition system.
2. Ensure ignition timing is correct.
3. Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector, fuel pressure regulator).
4. Check Electronic Control Module (ECM) and wiring.
5. Check airflow meter or vacuum sensor and wiring.
6. Check idle air control valve (if equipped) and wiring.
7. Check circuit opening relay and EFI main relay.
8. Check engine compression, valve clearance, valve timing and timing belt (if equipped).

Engine Difficult To Start Under Normal Conditions

1. Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
2. Ensure proper spark exists from ignition system.
3. Ensure ignition timing is correct.
4. Check engine compression, valve clearance, valve timing and timing belt (if equipped).
5. Check idle air control valve (if equipped) and wiring.
6. Check EGR system.
7. Check cold start injector system (if equipped).
8. Check coolant temperature sensor and wiring.
9. Check air temperature sensor and wiring.
10. Check Electronic Control Module (ECM) and wiring.

Engine Difficult To Start Under Cold Conditions

1. Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
2. Check coolant temperature sensor and wiring.
3. Check STA signal at Electronic Control Module (ECM).
4. Check idle air control valve (if equipped) and wiring.
5. Check cold start injector system (if equipped).
6. Check air temperature sensor and wiring.
7. Check Electronic Control Module (ECM) and wiring.

Engine Difficult To Start Under Hot Conditions

1. Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
2. Ensure ignition timing is correct.
3. Check fuel pressure control vacuum switching valve (if equipped) and wiring.
4. Check coolant temperature sensor and wiring.
5. Check idle air control valve (if equipped) and wiring.
6. Check cold start injector system (if equipped).
7. Check air temperature sensor and wiring.
8. Check Electronic Control Module (ECM) and wiring.

Incorrect Idle At Engine Start-Up

1. Check for defective throttle linkage or cable.
2. Check throttle opener or dashpot (if equipped).
3. Check idle-up vacuum switching valve (if equipped) and wiring.
4. Check idle air control valve (if equipped) and wiring.
5. Check coolant temperature sensor and wiring.
6. Check Electronic Control Module (ECM) and wiring.

Engine Idle Speed Remains High

1. Check for defective throttle linkage or cable.
2. Check dashpot or throttle opener (if equipped).
3. Check idle-up vacuum switching valve (if equipped) and wiring.
4. Check idle air control valve (if equipped) and wiring.
5. Check coolant temperature sensor and wiring.
6. Check air temperature sensor and wiring.
7. Check Throttle Position Sensor (TPS) and wiring.
8. Check A/C signal circuit to Electronic Control Module (ECM).
9. Check park/neutral switch signal to Electronic Control Module (ECM).
10. Check cold start injector system (if equipped).
11. Check fuel injectors.
12. Check Electronic Control Module (ECM) and wiring.

Engine Idle Speed Remains Low

1. Check coolant temperature sensor and wiring.
2. Check idle air control valve (if equipped) and wiring.
3. Check EGR system.
4. Check airflow meter or vacuum sensor and wiring.
5. Check fuel injectors.
6. Check Electronic Control Module (ECM) and wiring.

Rough Engine Idle

1. Check for vacuum leaks.
2. Check EGR system.
3. Ensure proper spark exists from ignition system.
4. Ensure ignition timing is correct.
5. Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
6. Check engine compression, valve clearance, valve timing and timing belt (if equipped).
7. Check coolant temperature sensor and wiring.
8. Check idle air control valve (if equipped) and wiring.
9. Check airflow meter or vacuum sensor and wiring.
10. Check Electronic Control Module (ECM) and wiring.

Engine Misfires

1. Check EGR system.
2. Ensure proper spark exists from ignition system.
3. Ensure ignition timing is correct.
4. Check engine compression, valve clearance, valve timing and timing belt (if equipped).
5. Check fuel injectors and cold start injector (if equipped).
6. Check airflow meter or vacuum sensor and wiring.
7. Check Electronic Control Module (ECM) and wiring.

Hesitation & Poor Acceleration

1. Ensure proper spark exists from ignition system.
2. Ensure ignition timing is correct.
3. Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
4. Check EGR system.
5. Check engine compression, valve clearance, valve timing and timing belt (if equipped).
6. Check Throttle Position Sensor (TPS) and wiring.
7. Check airflow meter or vacuum sensor and wiring.
8. Check coolant temperature sensor and wiring.
9. Check air temperature sensor and wiring.
10. Check oxygen sensor and wiring.
11. Check cold start injector system (if equipped).
12. Check Electronic Control Module (ECM) and wiring.

Engine Backfires

1. Ensure proper spark exists from ignition system.
2. Ensure ignition timing is correct.
3. Check valve timing and timing belt (if equipped).
4. Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
5. Check EGR system.
6. Check Throttle Position Sensor (TPS) and wiring.
7. Check airflow meter or vacuum sensor and wiring.
8. Check coolant temperature sensor and wiring.
9. Check air temperature sensor and wiring.
10. Check oxygen sensor and wiring.

Engine Surges

1. Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
2. Ensure proper spark exists from ignition system.
3. Ensure ignition timing is correct.
4. Check Electronic Control Module (ECM) and wiring.

Engine Knocks

1. Ensure ignition timing is correct.
2. Check knock sensor (if equipped) and wiring.
3. Check EGR system.
4. Check valve timing and timing belt (if equipped).
5. Check Electronic Control Module (ECM) and wiring.

Muffler Explosion

1. Ensure ignition timing is correct.
2. Check fuel-cut system.
3. Check cold start injector system (if equipped).
4. Ensure fuel injectors and fuel pressure regulator operate correctly.
5. Check coolant temperature sensor and wiring.
6. Check airflow meter or vacuum sensor and wiring.
7. Check Throttle Position Sensor (TPS) and wiring.
8. Check air temperature sensor and wiring.
9. Check oxygen sensor and wiring.
10. Check Electronic Control Module (ECM) and wiring.

Engine Stalls Soon After Start-Up

1. Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
2. Ensure proper spark exists from ignition system.
3. Check EGR system.
4. Check idle air control valve (if equipped) and wiring.
5. Check airflow meter or vacuum sensor and wiring.
6. Check coolant temperature sensor and wiring.
7. Check Electronic Control Module (ECM) and wiring.

Engine Stalls After Accelerator Is Depressed

1. Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
2. Ensure proper spark exists from ignition system.
3. Check airflow meter or vacuum sensor and wiring.
4. Check EGR system.
5. Check Throttle Position Sensor (TPS) and wiring.
6. Check Electronic Control Module (ECM) and wiring.

Engine Stalls After Accelerator Is Released

1. Check idle air control valve (if equipped) and wiring.
2. Check EGR system.
3. Check airflow meter or vacuum sensor and wiring.
4. Check Electronic Control Module (ECM) and wiring.

Engine Stalls When Shifting From Neutral Into Drive (A/T Models)

1. Check idle air control valve (if equipped) and wiring.
2. Check park/neutral switch signal to Electronic Control Module (ECM).

ENGINE HAS POOR FUEL ECONOMY

Check for vacuum leaks (oil filler cap, oil dipstick, hose connections, PCV hose, PCV valve and EGR system)

1. Check air filter.
2. Check idle speed.
3. Ensure proper spark exists from ignition system.
4. Ensure ignition timing is correct.
5. Check engine compression, valve clearance, valve timing and timing belt (if equipped).
6. Check EGR system.
7. Check dashpot or throttle opener (if equipped).
8. Check fuel-cut system.
9. Check fuel injectors.
10. Check cold start injector system (if equipped).
11. Check airflow meter or vacuum sensor and wiring.
12. Check coolant temperature sensor and wiring.
13. Check Throttle Position Sensor (TPS) and wiring.
14. Check oxygen sensor and wiring.
15. Check air temperature sensor and wiring.

Intermittent Simulation

To reproduce the conditions creating an intermittent fault, use the following methods

1. Lightly vibrate component. See «VIBRATION METHOD»(ref-21423-S15561294902001010300000) .
2. Heat component. See «HEAT METHOD»(ref-21423-S42880287952001010300000) .
3. Wiggle or bend wiring harness. See «VIBRATION METHOD»(ref-21423-S15561294902001010300000) .
4. Spray component with water. See «HUMIDITY METHOD»(ref-21423-S06787318112001010300000) .
5. Remove/apply vacuum source.

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic trouble codes. Use test results to identify a faulty component or circuit.

HEAT METHOD

Using hair dryer or similar device, apply heat to the component. Monitor suspected circuit or component while applying heat.

HUMIDITY METHOD

If humidity or moisture is suspected of causing intermittent failure, lightly spray water on the front of warm radiator to increase humidity in the engine compartment. Check for malfunction by monitoring suspected circuit or component with a DVOM.

If vehicle has interior water leakage, the water may have damaged the Electronic Control Module (ECM) or corroded the electrical connections. Carefully inspect ECM terminals and electrical connections for corrosion.

ELECTRICAL LOAD METHOD

To check if intermittent fault occurs under electrical load, turn on all electrical loads (heater blower, headlights, rear window defogger, wipers, etc.). Check for malfunction by monitoring suspected circuit or component with a DVOM.