1992 Pontiac Grand Prix 3.4L V6 DOHC high idle at cold start

CARTROUBLES

MEMBER
1992 PONTIAC GRAND PRIX

The car has around 87,000 miles. I am having trouble with the car idleing around 22-2500rpms with a cold start. It takes it about 15 minutes to idle down to the normal 900 or so rpms. During this time the rpms ocassionally spike, and the service engine soon light will come on. I replaced the IAC, which didn't help. I borrowed a scan tool which seemed to show the oxygen sensor is fine. It did show the car is running between rich and lean frequently. I found info on other sites regarding a common issue with this engine similar to mine, and replacing the intake manifold gaskets seemed to fix it. This is something I feel is out of my league, and am wondering if anyone out there thinks this makes sense and is something I should shell the cash out for. Should I try the oxygen sensor first, even though the tool says it seems okay. What is up with the rich lean deal? The check gauges light is also on frequently, even though the gauges appear normal. Any ideas? The antilock light is also coming on occasionally. The brake lights went out completely a few weeks ago. I replaced the fuse, and they work fine, but the antilock light is still coming on occasionally. Any ideas about that one.
Thanks for taking the time to read this post. Any help is, of course, greatly appreciated.

2 Replies

JPTRUAX

MEMBER
18 POSTS

Sounds like a vacuum leak, which could be a vacuum line or intake gasket, so yes it makes sense. To check it, start it up and spray carb cleaner around the intake where the gasket is, if the motor revs up at any time you found your problem. If the does not do it spray the vacuum lines. As for the anti lock, it could be anything from a sensor to air in the line. Could even be moister around the sensor. Hope this helps!