Engine Controls - Tests W/o Codes: Other Volkswagen Passat B4

ENGINE DOES NOT START OR IS DIFFICULT TO START WHEN COLD

1. Check fuel quality.
2. Check fuel pump relay and fuel pump.
3. Check auxiliary air intake system.
4. Check fuel system acceleration enrichment circuits.
5. Check cold-start valve.
6. Check MAF sensor.
7. Check sensor plate rest position and idle circuit.
8. Check fuel system differential and residual pressures.
9. Check fuel injection volume.
10. Check engine coolant temperature sensor.
11. Check ignition timing, spark plugs, distributor, secondary ignition wiring and coil.
12. Check Hall Effect sensor.
13. Check ignition coil power output stage.

ENGINE DOES NOT START OR IS DIFFICULT TO START WHEN WARM

1. Check radiator cooling fan after-run circuit.
2. Check fuel pump check valve.
3. Check fuel evaporative frequency solenoid(s).
4. Check fuel system for leaks.
5. Check auxiliary air intake system.
6. Check idle speed.
7. Check fuel system acceleration enrichment circuits.
8. Check cold-start valve.
9. Check injector fuel pressure and volume.
10. Check sensor plate rest position and idle circuit.
11. Check sealing ring under control plunger.
12. Check fuel system differential and residual pressures.
13. Check engine coolant temperature sensor.
14. Check ignition timing, spark plugs, distributor, secondary ignition wiring and coil.

UNEVEN IDLE OR NO IDLE WITH COLD ENGINE OR DURING WARM-UP

1. Check fuel evaporative frequency solenoid(s).
2. Check auxiliary air intake system.
3. Check idle speed.
4. Check HO2S control circuit.
5. Check cold-start valve.
6. Check injector fuel pressure and volume.
7. Check TP sensor.
8. Check fuel system differential and residual pressures.
9. Check engine coolant temperature sensor.
10. Check exhaust system.
11. Check ignition timing and spark plugs.

ENGINE STARTS BUT STALLS

1. Check fuel pump relay and fuel pump.
2. Check auxiliary air intake system.
3. Check idle speed.
4. Check MAF sensor.
5. Check sensor plate rest position and idle circuit.
6. Check fuel system differential and residual pressures.
7. Check idle switch.
8. Check engine coolant temperature sensor.

POOR ACCELERATION WITH COLD ENGINE OR DURING WARM-UP

1. Check fuel pump.
2. Check auxiliary air intake system.
3. Check HO2S control circuit.
4. Check fuel system acceleration enrichment circuits.
5. Check MAF sensor.
6. Check TP sensor.
7. Check fuel system differential and residual pressures.
8. Check injector fuel pressure and volume.
9. Check idle switch.
10. Check engine coolant temperature sensor.
11. Check throttle body basic adjustment.
12. Check exhaust system.
13. Check ignition timing, spark plugs, distributor, secondary ignition wiring and coil.

ENGINE STALLS WHILE DRIVING

1. Check fuel pump.
2. Check auxiliary air intake system.
3. Check injector fuel pressure and volume.
4. Check idle and full throttle switches.
5. Check intake air preheating system.
6. Check ignition timing, spark plugs, distributor, secondary ignition wiring and coil.

POOR PERFORMANCE

1. Check fuel pump.
2. Check throttle cable adjustment.
3. Check auxiliary air intake system.
4. Check MAF sensor lever adjustment and control plunger.
5. Check TP sensor.
6. Check fuel system differential and residual pressures.
7. Check injector fuel pressure and volume.
8. Check full throttle switch.
9. Check intake air preheating system.
10. Check catalytic converter.
11. Check ignition timing.

ENGINE RUN-ON (DIESELING)

1. Check fuel evaporative frequency solenoid(s).
2. Check fuel system for leaks.
3. Check cold-start valve.
4. Check injector fuel pressure and volume.
5. Check MAF sensor lever adjustment and control plunger.

HIGH FUEL CONSUMPTION

1. Check fuel system for leaks.
2. Check HO2S control circuit.
3. Check cold-start valve.
4. Check injector fuel pressure and volume.
5. Check MAF sensor.
6. Check TP sensor.
7. Check injector fuel pressure and volume.
8. Check full throttle switch.
9. Check intake air preheating system.
10. Check exhaust system for leaks (between cylinder and HO2S).
11. Check ignition timing.

ENGINE KNOCK

1. Check knock sensor(s).
2. Check full throttle switch.
3. Check ignition timing.

ENGINE RUNS UNEVENLY OVER ENTIRE SPEED RANGE

1. Check auxiliary air intake system.
2. Check injector fuel pressure and volume.
3. Check ignition timing, spark plugs, distributor, secondary ignition wiring and coil.

Intermittent Simulation

To reproduce conditions creating intermittent fault, use following methods

1. Lightly vibrate component.
2. Heat component.
3. Wiggle or bend wiring harness.
4. Spray component with water.
5. Remove/apply vacuum source.

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.