cars rpms go up and down when idleing. car has new cats and o2 sensors and check engine light is not showing anything is wrong?
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2004 Pontiac Grand Prix Question: rpms go up and down when idleing
Answer #1Russ March 25, 2009, 23:49Master
The cause of an idle surge can sometimes be hard to pinpoint. A sensor could be failing but not enough to turn the check engine light on. You may have a dirty throttle body or a fuel injector issue. This problem may need to be checked out by a qualified technician. If you don't have a regular shop that does your repairs check out the listings at www.repairpal.com.
Visitor, May 17, 2010, 11:32
I had the same problem with my car start about 2 months ago and thought it was the O2 sensor as well, but it turns out it was the mass flow air sensor instead.