engine rocking at warm idle speed

1999 PONTIAC GRAND AM
148,000 MILES • 2.4L • 4 CYL • FWD • AUTOMATIC
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DENNYL12
  • MEMBER
  • 2 POSTS
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.
Aug 16, 2014 at 1:35 AM
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HMAC300
  • ✓Experienced Mechanic
  • 48,601 POSTS
clean throttle plate on both sides and iaac hole with choke cleaner then check for a vacuum leak
Aug 16, 2014 at 3:04 AM
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DENNYL12
  • MEMBER
  • 2 POSTS
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.
Aug 16, 2014 at 6:27 AM
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HMAC300
  • ✓Experienced Mechanic
  • 48,601 POSTS
usually it will throw a misfire code if it's that bad. check fuel pressure then do compression test
Aug 16, 2014 at 8:28 AM
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