1992 Pontiac Grand Prix


Old 12-03-04, 09:30 AM
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Question 1992 Pontiac Grand Prix rough idle

My 1992 Pontiac Grand Prix STE 3.4L eng Automatic transmission with 37,000 miles is having a bad Idling problem. When I starts it the engine revs up to 2500-3000 rmp and does not idle down for a long time. I've changed the Idle control selenoid, checked for vacume leaks but it still does the same thing. I will start driving it and about 20 min later the car would then idle down and idle rough. If I shut the engine off and restart it after 5 min it idles nice and smooth. Could you enlighten me as to what may be the problem.

Last edited by jsingh; 12-03-04 at 03:37 PM.
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Old 12-03-04, 04:01 PM
Join Date: Apr 2002
Location: Pittsburgh,Pa
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Is the check engine light on?If so we will need codes to continue,if not check for binding throttle or trans cables.Has the battery been dead or replaced before this began to occur?
Old 12-10-04, 08:57 AM
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1992 Pontiac Grand Prix rough idle

My Mechanic had checked it for a code and he replaced the Automatic Idle control selonoid. He also mentioned that he had the intake off to check for vacume leaks. Originally the vacume hose to the brake booster had a hole so I replaced it. The process for me involved taking off the intake but the car ran fine after that, then I was in a fender bender and the car sat for a while and the battery ran down but was not completely dead. After this that was whenever I started it up it would idle at 2500 for a while then after a while(driving) it would go down to normal idle but with a missing feeling. If I shut the engine off for a few minutes then start it back up it idles and run fine. After he replaced the selonoid with a used one the car never ran right. I bought a new one but it still runs does the same thing.
Old 12-10-04, 01:56 PM
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Those engines were famouse for intake gaket failure, not the upper intake, but the lower. This would cause the symptems you have.

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