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car shakes when idling?

my car sat for 3 weeks without being driven and now it shakes really bad when idling. it has even stalled. its a pontiac sunfire 2.2L OHV. it does not do it at all while im driving but as soon as i stop it gets really bad. when it shakes, the RPM's go way down and the lights dim.

Update:

it has brand new plugs and wires as of 500 miles ago. it ran perfectly fine until it sat for 3 weeks straight.

4 Answers

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  • 1 decade ago
    Favorite Answer

    You can be sure the engine is misfiring. You don't mention a check engine light so I assume it is a 1995 Sunfire, and that means you have a conventional distributor, too. A good place to start is with replacing the distributor cap (may as well change the rotor while you are at it) and the plugs. If the misfire continues the spark plug wires are the next step - they are expensive so I saved them for last but a proper tune-up involves replacing all the parts I listed. A bottle of fuel injector cleaner in the tank is a good thing, too.

    If after all this the engine still misfires you will need to do some serious troubleshooting, starting with unplugging one fuel injector at a time to identify the one that doesn't do anything. That injector is probably dead. The injector will probably have to be replaced, but it can be tested at many larger auto parts shops.

    Source(s): 35 years maintaining my own cars
  • 1 decade ago

    It could be the torque converter.

    Most late-model automatics have some type of lockup torque converter to improve fuel economy. If the lockup fails to engage, there will be some slippage and fuel economy will drop. Causes here include a bad lockup solenoid, incorrect sensor input information to the transmission controller or PCM (typically a speed sensor) and hydraulic control problems. If the lockup fails to release, the engine may shudder and die when coming to a stop. Causes here include a faulty lockup solenoid, a sticking lockup valve, grounded lockup solenoid wiring or a missing lockup solenoid spacer plate screen.

    Lockup shudder is another complaint that may be encountered. This refers to a vibration that is felt just before or after lockup occurs. This kind of problem can be hard to diagnose because the cause may be the torque converter, transmission or engine. Bad motor mounts, engine misfire, a bad CV-joint or U-joint, etc. can all cause vibrations that may be felt as a shudder throughout the drivetrain.

    Source(s): 30 yrs working on cars and Mech Eng http://www.aa1car.com/library/torque_converters.ht...
  • Anonymous
    1 decade ago

    is the check engine light on? and if so is it newer than 1996 if so bring it to your nearest autozone or pepboys and theyll hook it up to a scanner and tell you whats wrong with it for free

  • 1 decade ago

    u most likely need 2 give it tune up new plugs & wires i suggest and also check your oil level

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