2002 GMC Envoy RPM's fluctuate upon activating AC

65PONTIAC

MEMBER
2002 GMC ENVOY
6 CYL
2WD
AUTOMATIC
125,000 MILES

Everytime I activate my AC system the cars RPM's takes a dip and almost stalls before the systems computer compensates and raises RPM's. Then the RPM's dip again almost to stall and raises again. This occurs over and over at idle. The truck may eventually stall at times where the computer doesn't compensate before the RPM's drop too low. Could this be due to some time of solenoid which should turn on when the AC is turned on?

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,758 POSTS

Actually, the computer should adjust for it through a throttle position sensor (TPS). It may be going bad. Has the check engine light come on?

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Wednesday, August 26th, 2009 AT 9:23 PM

65PONTIAC

MEMBER
4 POSTS

No check engine light has come on. This problem has been for over a year old. I just don't use my AC to avoid this issue. Could it be due to a dirty throttle body?

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Thursday, August 27th, 2009 AT 1:19 PM

JACOBANDNICKOLAS

MECHANIC
109,758 POSTS

I would say no to dirty injectors. It would do it all of the time if that was the problem. I still say the TPS is the problem, but that is a guess without a code. Has anyone checked it for that problem?

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Thursday, August 27th, 2009 AT 4:05 PM

65PONTIAC

MEMBER
4 POSTS

I have not taken it to a shop, low on funds. But I am living with out AC for the meantime. Last year my truck had a check engine light after I had oil change service and they checked for codes. The only thing that came up was my Temp sensor. So I planned to try to change the sensor on the weekend but the check engine light went away the following day. Any ideas? As of now my truck runs smooth and only has engine problems when using the AC.

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Thursday, August 27th, 2009 AT 5:29 PM

JACOBANDNICKOLAS

MECHANIC
109,758 POSTS

Chances are the temp sensor won't fix this problem. It is designed to tell the computer how rich to make the fuel mixture based on ambient temps. It won't hurt to try it, but as I said, I don't know if it will fix this problem.