Engine Controls - Tests W/o Codes: Other BMW 5 series E34

NO START - COLD ENGINE

1. Ensure spark plugs fire.
2. Check ignition and sensor wires for proper connection.
3. Check ignition coil circuit.
4. Ensure fuel pressure is correct.
5. Check fuel injectors.
6. Check airflow sensor.
7. Check engine speed (reference point) sensor.
8. Check cylinder identification sensor.
9. Check vehicle (road) speed sensor.
10. Check DME/Motronic control unit.

STARTS BUT STALLS - COLD ENGINE

1. Check ignition and sensor wires for proper connection.
2. Check fuel injectors.
3. Check DME/Motronic control unit.

HARD TO START - COLD ENGINE

1. Ensure spark plugs fire.
2. Check distributor.
3. Ensure fuel pressure is correct.
4. Check DME/Motronic control unit.

NO START - WARM ENGINE

1. Ensure fuel pressure is correct.
2. Check fuel injectors.
3. Check DME/Motronic control unit.
4. Check engine speed (reference point) sensor.
5. Check cylinder identification sensor.
6. Check ignition and sensor wires for proper connection.
7. Ensure spark plugs fire.
8. Check ignition and coil circuit.

ERRATIC IDLE - WARM-UP

1. Check throttle position switch and connection.
2. Check coolant temperature sensor and connection.
3. Check idle actuator and idle (air) control valve.
4. Check DME/Motronic control unit.
5. Check air temperature sensor and airflow sensor.
6. Check coolant temperature sensor.
7. Ensure spark plugs fire.
8. Check ignition and sensor wires for proper connection.
9. Check distributor.
10. Check ignition and coil circuit.
11. Check intake system.
12. Check coolant.

BACKFIRING

1. Check fuel injectors.
2. Ensure ignition timing is correct.
3. Check DME/Motronic control unit.
4. Check distributor.
5. Ensure spark plugs fire.
6. Check ignition and coil circuit.
7. Check exhaust system.

INCORRECT IDLE SPEED

1. Check fuel injectors.
2. Check DME/Motronic control unit.
3. Check intake system.
4. Check throttle position switch.
5. Check coolant temperature sensor.
6. Check distributor.

OFF-IDLE HESITATION

1. Check fuel injectors.
2. Check DME/Motronic control unit.
3. Check ignition and sensor wires for proper connection.
4. Check distributor.
5. Ensure spark plugs fire.
6. Check ignition and coil circuit.

KNOCKING

1. Check DME/Motronic control unit.
2. Check ignition and coil circuit.
3. Ensure spark plugs fire.
4. Check ignition and coil circuit.

COASTING HESITATION

1. Check fuel injectors.
2. Check DME/Motronic control unit.
3. Check ignition and sensor wires for proper connection.

ENGINE MISFIRE - ALL CONDITIONS

1. Check fuel injectors.
2. Check DME/Motronic control unit.
3. Check ignition and sensor wires for proper connection.
4. Check ignition and coil circuit.
5. Check intake and exhaust system.
6. Check for vacuum leaks.

INSUFFICIENT ENGINE POWER

1. Check fuel injectors.
2. Ensure fuel pressure is correct.
3. Check DME/Motronic control unit.
4. Check airflow sensor.
5. Check for restricted exhaust.
6. Check throttle position switch.
7. Check coolant temperature sensor.
8. Check air temperature sensor.
9. Check ignition and coil circuit.
10. Check intake and exhaust system.

POOR FUEL ECONOMY

1. Check for leaky fuel injectors.
2. Check for faulty oxygen sensor.
3. Check for poor wire connections and faulty spark plugs.
4. Check for malfunctioning intake system.

EXCESSIVE EMISSIONS (HC & NOx)

1. Check for leaky fuel injectors.
2. Check DME/Motronic control unit.
3. Check for faulty oxygen sensor.
4. Check ignition and sensor wires for proper connection.
5. Check intake system.

Intermittent Simulation

To reproduce the conditions creating an intermittent fault, use the 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.