1997 Pontiac Bonneville Engine Reving while cold

SKURIOUS

MEMBER
1997 PONTIAC BONNEVILLE
6 CYL
FWD
AUTOMATIC
134,000 MILES

It has recently gotten cold outside and when I go to start my car for the first time of the day, it will start as normal, but shortly after the rpm will start to drop but the engine revs up. It does this until the engine warms up or until I start driving it. When im driving it doesnt do this. I am due for an oil change but im not sure if this would affect this at all. Thanks.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

The oil change won't help. Has the check engine light come on? It sounds like a throttle position sensor (TPS) or the coolant temp switch. These are both a guess without the check engine light.

If the light has come on, have the computer scanned at a nationally recognized parts store. Most will do it for free and it will identify where the problem is coming from.

Let me know.

Joe

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Tuesday, December 15th, 2009 AT 10:28 PM

SKURIOUS

MEMBER
2 POSTS

No light comes on at all. After it warms up or I drive it for a bit it will stop doing it. You said something about a coolant temp sensor. I am replacing the water pump soon because it is leaking could this have something to do with it?

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Tuesday, December 15th, 2009 AT 11:44 PM

DANAUTHIER

MECHANIC
156 POSTS

Jacobandnickolas Is/are correct, the oil change will not help. Are you sure the water pump is leaking.

The 3.8 litre engine in you vehicle is known for the intake leaking. The intake maniflold is made of plastic and degrades ove time (135k) and will leak coolant and/or oil. The leaking intake is often mistaken for a water pump leak on this engine and the leaking intake will cause the high idle untill the engine warms up.

Give us a little more info and we will be glad to help you out.

Thank you,

Dan

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Wednesday, December 16th, 2009 AT 12:10 AM