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Idle speed oscillates

dwightolson
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dwightolson Member

dwightolson

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Posted (edited)

I've had an idle speed problem since I bought my 1999 C2 two years ago. The idle speed oscillates between about 500 and 1000 rpm with the AC off. What complicates matters is that it only does it about 25% of the time. It will do it at one stop light and not at the very next for example. Doesn't seem to have to be at full operating temperature sensitive (although it's never done it right after a cold start, it has done it before it's fully warmed up).

I've taken it to 2 dealers. Both the idle speed control and the throttle position switch have been replaced. The throttle body has been cleaned numerous times. The last dealer said there are no fault codes.

Any other ideas would be welcome.

thanks

Dwight

Edited by dwightolson
  • 2 months later...
dwightolson Member

dwightolson

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  • Author
Posted
Are you sure they did what they said?

If so, unplug the MAF and see if idle and low speed running are affected.

Thanks again, Loren.

I unplugged the MAS and it seemed a little different but not much - the idle seemed to come down more slowly and kind of hang around 1000 rpm for a bit. So, I replaced the MAS. Then I did the one minute on and ten seconds off routine to reset the computer. Didn't fix the problem. So, I'm kind of at a loss again since I've replaced the throttle position switch, the idle speed control and now the MAS.

Would appreciate any other recommendations you might have.

thank you much

Dwight

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Loren Member

Loren

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  • Admin
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At this point you need to put it on a scan tool that can read TRA, FRA and air flow (over the MAF).

With these numbers you should be able to see what is really going on.

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