Engine Control System Tests W/o Codes: Other Lexus LX J80

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 position 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 engine compression, valve clearance, valve timing and timing belt (if equipped).
5. Check airflow meter or MAP sensor and wiring.
6. Check idle air control valve (if equipped) and wiring.
7. Check circuit opening relay and EFI main relay.
8. Check STA signal at Engine Control Module (ECM).
9. Check Engine Control Module (ECM) and wiring.

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 STA signal at Engine Control Module (ECM).
5. Check engine compression, valve clearance, valve timing and timing belt (if equipped).
6. Check idle air control valve (if equipped) and wiring.
7. Check EGR system.
8. Check cold start injector system (if equipped).

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 STA signal at Engine Control Module (ECM).
3. Check idle air control valve (if equipped) and wiring.
4. Check cold start injector system (if equipped).

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 idle air control valve (if equipped) and wiring.
5. Check cold start injector system (if equipped).
6. Check STA signal at Engine Control Module (ECM).

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 Engine Control Module (ECM) and wiring.
6. Check Throttle Position (TP) sensor and wiring.
7. Check A/C signal circuit to Engine Control Module (ECM).
8. Check park/neutral position switch signal to Engine Control Module (ECM).
9. Ensure dipstick and oil filler cap are properly seated.

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 Throttle Position (TP) sensor and wiring.
6. Check A/C signal circuit to Engine Control Module (ECM).
7. Check park/neutral position switch signal to Engine Control Module (ECM).
8. Check cold start injector system (if equipped).
9. Check fuel injectors.
10. Check Engine Control Module (ECM) and wiring.

Engine Idle Speed Remains Low

1. Check idle air control valve (if equipped) and wiring.
2. Check airflow meter or MAP sensor and wiring.
3. Check fuel injectors.
4. Check Engine 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 airflow meter or MAP sensor and wiring.
8. Check Engine Control Module (ECM) and wiring.
9. Ensure dipstick and oil filler cap are properly seated.

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).

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 (TP) sensor and wiring.
7. Check airflow meter or MAP sensor and wiring.
8. Check oxygen sensor and wiring.
9. Check cold start injector system (if equipped).
10. Check Engine 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 (TP) sensor and wiring.
7. 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 Engine 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 Engine 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 Throttle Position (TP) sensor and wiring.
6. Check oxygen sensor and wiring.
7. Check Engine 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 Engine 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 EGR system.
4. Check Throttle Position (TP) sensor and wiring.
5. Check Engine 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 Engine 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 position switch signal to Engine Control Module (ECM).

Intermittent Simulation

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

1. Lightly vibrate component. See «VIBRATION METHOD»(ref-21968-S09766931982001010300000) .
2. Wiggle or bend wiring harness. See «VIBRATION METHOD»(ref-21968-S09766931982001010300000) .

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