Misfiring at idle replaced plugs and coils?

Tiny
STRANGEMADNESS
  • MEMBER
  • 2000 PONTIAC GRAND AM
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 206,000 MILES
So, I replaced plugs and coils and a bad o2 sensor. And IAT sensor because the car runs fine with it unplugged, but replacement made it very slightly better. Car misses at idle and idles around 500-600 RPMs with occasional dips to 300ish. With A/C on idle remains the same and dips at first before going back to its spot. Desired idle reads 600 rpms and sometimes 500. With IAT unplugged it reads 900 desired and runs really smooth. What could be the issue, IAC valve? Are there any relearn steps? Replaced the alternator and battery was dead for a minute. Sometimes stalls when coming to a stop.
Friday, September 13th, 2024 AT 8:13 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
A misfire at idle is indicated you may have low compression in one or more of the cylinders, please go over this guide for more information:

https://www.2carpros.com/articles/repairing-engine-rough-idle-issues

Here is how to do a compression test which I would do as well:

https://www.2carpros.com/articles/how-to-test-engine-compression

Please go over these guides and get back to us.

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Friday, September 13th, 2024 AT 11:02 AM

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