Home ReviewsRefund
Home/BMW/5 series/BMW 5 series E39 (1995-2000)/Repair manual/Testing & Diagnostics/Engine Controls - Tests W/o Codes: Other
Contents Wiring diagrams Section: Testing & Diagnostics All sections

Engine Controls - Tests W/o Codes: Other BMW 5 series E39

Testing & Diagnostics ~331 words

ENGINE DOES NOT START (WILL NOT CRANK)

  1. Loose or corroded battery terminals.
  2. Ensure battery is fully charged.
  3. Starter motor inoperative.

ENGINE CRANKS, BUT FAILS TO START

  1. Starter motor rotating too slowly.
  2. Ignition system malfunction.
  3. DME/Motronic control unit malfunction.
  4. Insufficient fuel pressure.

ENGINE BACKFIRES

  1. Air leak into/from exhaust system.
  2. Intake manifold vacuum leak.
  3. Burned valve.
  4. Lean air/fuel mixture.
  5. Incorrect ignition timing.
  6. Incorrect valve timing.

LOSS OF POWER

  1. Insufficient fuel pressure.
  2. Restricted fuel filter.
  3. Restricted air filter.
  4. Ensure engine compression is okay.
  5. Ignition system malfunction.
  6. Burned or sticking valves.
  7. Restricted exhaust system.
  8. DME/Motronic control unit malfunction.
  9. Incorrect valve timing.

DETONATION (ENGINE KNOCK)

  1. Ignition timing too far advanced.
  2. Blown head gasket.
  3. Stuck thermostat (engine overheating).
  4. Lean fuel mixture.
  5. DME/Motronic control unit malfunction.
  6. No coolant in radiator/engine (engine overheating).
  7. Wrong octane fuel.

STALLS AT IDLE

  1. Insufficient fuel pressure
  2. DME/Motronic control unit malfunction.
  3. Incorrect ignition timing.
  4. Blocked or restricted exhaust system.

ENGINE RUNS ROUGH (OFF IDLE)

  1. Fouled spark plugs
  2. Burned or sticking valve.
  3. Ignition system malfunction.
  4. Intake manifold air leak.
  5. Fuel injector not operating.
  6. DME/Motronic control unit malfunction.
  7. Blown head gasket.

ROUGH OR UNSTABLE IDLE

  1. Fouled spark plugs
  2. Burned or sticking valves.
  3. Intake manifold air leak.
  4. Incorrect valve timing.
  5. Ignition system malfunction.
  6. Fuel injector not operating.
  7. DME/Motronic control unit malfunction.
  8. Blown head gasket.

ENGINE MISFIRES - ALL CONDITIONS

  1. Fouled spark plugs
  2. Burned or sticking valves.
  3. Ignition system malfunction.
  4. Fuel injector not operating.
  5. DME/Motronic control unit malfunction.
  6. Blown head gasket.

POOR FUEL ECONOMY

  1. Leaking fuel injectors.
  2. Faulty oxygen sensor.
  3. DME/Motronic control unit malfunction.

EXCESSIVE EMISSIONS

  1. Leaking fuel injectors.
  2. DME/Motronic control unit malfunction.
  3. Faulty oxygen sensor.
  4. Faulty mass airflow sensor.
  5. Faulty temperature sensor.

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 mist.
  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.

More articles — Engine Controls - Tests W/o Codes