ENGINE ROCKING AT WARM IDLE SPEED

  • Tiny
  • DennyL12
  • 1999 Pontiac Grand Am
  • 2.4L
  • 4 CYL
  • FWD
  • automatic
  • 148,000 miles

When the engine is cold the idle is 1000 rpm and the engine runs fine but when it warms up it drops down to 500 rpm and the engine rocks like it has a misfire.

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Saturday, August 16th, 2014 AT 8:35 AM

3 Replies

  • Tiny
  • hmac300
  • Expert
  • 44,425 posts

Clean throttle plate on both sides and iaac hole with choke cleaner then check for a vacuum leak

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Saturday, August 16th, 2014 AT 10:04 AM
  • Tiny
  • DennyL12
  • Member

I already cleaned the throttle body and replaced the IAC valve. I also checked for vaccum leaks but it still was rattling an shaking a lot to the point where I could see it but the car is not throwing any codes.

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Saturday, August 16th, 2014 AT 1:27 PM
  • Tiny
  • hmac300
  • Expert
  • 44,425 posts

Usually it will throw a misfire code if it's that bad. Check fuel pressure then do compression test

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Saturday, August 16th, 2014 AT 3:28 PM

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