Engine revving on its own? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 05-09-2010, 04:49 AM   #1
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Default Engine revving on its own?

Tonight, when I started her up, (97 SSE), the engine revved and the rpms shot up to 3000 for about 2 or 3 seconds. Happened 2/3 times I started it. No drivability problems and no check engine light.

Throttle position sensor? Or what? Haven't done anything to it recently.
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Old 05-09-2010, 09:08 AM   #2
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IAC stuck open more than it should be???
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Old 05-09-2010, 10:29 AM   #3
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Originally Posted by jdaniels View Post
Tonight, when I started her up, (97 SSE), the engine revved and the rpms shot up to 3000 for about 2 or 3 seconds. Happened 2/3 times I started it. No drivability problems and no check engine light.

Throttle position sensor? Or what? Haven't done anything to it recently.
The same thing happens with my 97 SE.I'm going to replace the IAC today and check my fuel pressure due to the fact that I've been getting P0171 codes and I'm suspecting a weak fuel pump.I'll let you know if the IAC fixes the revving.
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Old 05-09-2010, 11:20 AM   #4
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Surging RPM can be a vacuum leak, stuck IAC, dirty throttle body. Check each of those and I'm sure the problem will be found.
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Old 05-09-2010, 11:21 AM   #5
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Try cleaning the IAC pintle with carb & choke cleaner first. The P0171 could be a dirty MAF sensor, or a vac leak somewhere.
https://www.gmforum.com/showthread.p...ighlight=p0171
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Old 05-09-2010, 11:29 AM   #6
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I just added another check to the P0171 code, check for loose MAF and IAC sensors. Both are open to the vacuum, and the IAC has a O ring that should be checked.
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Old 05-12-2010, 01:55 AM   #7
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Got an engine light tonight, will run it tomorrow and see what'* up.
Where is the IAC?
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Old 05-12-2010, 07:05 AM   #8
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Here is your IAC. Just to the left of your MAF sensor.


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Old 05-12-2010, 11:15 AM   #9
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This is going to be the most oblivious and ridiculous post ever, I know, and I haven't gone out and tried, so it may very well be easy..

But I'm assuming all of this (MAF, IAC) requires me to take the engine cover off, correct? (The grey plastic piece labelled 3800) How would I do this?
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Old 05-12-2010, 11:26 AM   #10
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Originally Posted by jdaniels View Post
This is going to be the most oblivious and ridiculous post ever, I know, and I haven't gone out and tried, so it may very well be easy..

But I'm assuming all of this (MAF, IAC) requires me to take the engine cover off, correct? (The grey plastic piece labelled 3800) How would I do this?
Remove oil cap, pull upwards.
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