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Troubleshooting Engine Performance Problems Part 9

• The engine will not idle smoothly, or it stalls during idle when the engine is warm:
  When the engine is warm or hot and you take your foot off the gas pedal, the engine runs very rough and may even stall. When you run the engine at higher speeds, it seems to run fine.

  Possible causes:
  

  1. If you have a carburetor, you may have a bad accelerator pump or power circuit: Replace accelerator pump or replace carburetor.

  2. There may be a vacuum leak: Check and replace vacuum lines as required.

  3. The fuel pressure regulator may be operating at too low a pressure: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (Generally not a DIY job)

  4. Idle speed set incorrectly: Set idle speed to specs.

  5. There may be some type of ignition problem: Check and replace distributor cap, rotor, ignition wires and spark plugs.

  6. There may be a fault in the computerized engine control system: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)

  7. The EGR valve may be bad: Replace EGR valve.

  8. The engine may have mechanical problems: Check compression to determine engine condition.

  9. The fuel injectors may be dirty: Clean or replace fuel injectors.

  ~~~~~~~~~~

• The engine idles too fast:
  After the engine and it has run long enough to be warm, the idle speed does not come down to normal. You really notice it when you come to a stop and must have to push hard on the brake pedal to keep the car from moving

  Possible causes:
  

  1. If you have a carburetor, you may have a bad accelerator pump or power circuit: Replace accelerator pump or replace carburetor.

  2. The engine may be overheating: Check and repair cooling system

  3. The fuel pressure regulator may be operating at too low a pressure: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (Generally not a DIY job)

  4. The ignition timing may be set wrong: Adjust ignition timing.

  5. There may be some type of ignition problem: Check and replace distributor cap, rotor, ignition wires and spark plugs.

  6. There may be a fault in the computerized engine control system: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)

  7. There may be a vacuum leak: Check and replace vacuum lines as required.

  8. . You have a bad idle speed control unit: Replace idle speed control unit

  9. The alternator may not be working properly: Replace alternator.

  ~~~~~~~~~~

• The car uses more oil than normal, but there is no trace of smoke from the exhaust:
  The oil level is low between oil changes. You never noticed it before and it doesn't appear that the oil is being burned by the engine. There is not a trace of smoke in the exhaust.

  Possible causes:
  

  1. The PCV system is not working properly: Replace PCV valve.

  2. The engine may have mechanical problems: Check compression to determine engine condition.

  3. The engine's valve seals may be worn: Replace valve seals. (Generally not a DIY job)

  4. The engine's gaskets and seals may be damaged: Replace gaskets and seals as required.

  More... » Part 1       » Part 2       » Part 3       » Part 4 » Part 5       » Part 6       » Part 7       » Part 8 » Part 9       » Part 10

  Additional Information provided courtesy of
  ALLDATAdiy.com and Warranty Direct
  © 2000-2007 Vincent T. Ciulla

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