1998 Pontiac Grand Prix I have a Pontiac Grand Prix GTP sup

BEBOP

MEMBER
1998 PONTIAC GRAND PRIX
6 CYL
FWD
AUTOMATIC
150,000 MILES

I have been experiencing some rough idle with my car lately and the rpm seems low also at idle often under 1000rpm. I recently replaced the spark plugs and cables so I dont think its that and I had a fuel leak fixed recently as well. So I really can't figure out what it would be. I am thinking it might be the catalytic converter since I havent changed that since I got the car and I bought it used so it might be a possibility and my boost idicater does not show any boost anymore so I dont know what that might be either. Anyways I just need somone to point me in the general direction of what I should probably do. I am a college student so I dont have that much money to spend. Please help.

Tuesday, April 7th, 2009 AT 11:45 AM

2 Replies

JAMES W.

MECHANIC
2,394 POSTS

Normal for your car should be around 750 rpm. At 1000, your a little high. The possible cause of both high and rough idle could be a vacuum leak. Check all your vacuum hoses for cracks, splits or rotted ends where they attach to the engine intake manifold.
Do you have, or have you had, a check engine light? If yes, you will need to have the ECM scanned to retrieve the stored code from ECM memory and pass them on to us. We can go from there. Please advise.

Was this

answer

helpful?

Yes

No

Tuesday, April 7th, 2009 AT 1:06 PM

BEBOP

MEMBER
2 POSTS

Ok I will check the hoses when I get back from school. Also yes I have had a check engine light come on before, will look into getting that stored code as soon as possible.

Was this

answer

helpful?

Yes

No

Wednesday, April 8th, 2009 AT 8:32 AM