93 Grand Prix Rough Idle


Asked by Mar 01, 2013 at 07:48 AM about the 1993 Pontiac Grand Prix 2 Dr SE Coupe

Question type: Maintenance & Repair

8 Answers


I am working on a 93 Grand prix with a 3.1. I just installed the motor. it started right up and ran fine until it started to warm up and come down to its low idle. the warmer it gets the rougher the idle. if you give it a little fuel or drive it, clears right up and has plenty of power. I changed the the following parts most of the used from the other motor. idle sensor, throtle position sensor, coil pack, new plugs and wires, EGR valve, pcv valve, Fuel presure regulator, new fuel filter, New Fuel pump(old one had low presure), Purge silinoid, Map sensor. None of these things have had any affect. Not sure what to look at next. Any help would be apreaciated.

1 of 1 people found this helpful.

It sounds like you covered everything. Try getting the codes read to see if any are pending. Good luck.


No codes


Being a 93.. Codes rarely come up.. Unless it is something to do with the emissions system.. When you replaced the coil packs, did you check the ignition control module (the flat plate they snap onto) for damage. Also, the knock sensor located on the lower rear of the motor. Make sure it is connected and the connector is not loose or damaged. Are you getting any smoke from the exhaust when it starts running rough?


I asked about the knock sensor, because when I had to swap the 3.1 in my 93 z24, I accidentally broke the clip for the knock sensor and when it came loose the car would start running like crap at idle, but would drive just fine.. Sounds quite similiar to your symptoms.

1 of 1 people found this helpful.

Thanks for a fresh idea. But it seems well connect and ok. I put the complete base and coils on. There is no smoke


Your problem just sounds so much like my knock sensor issue I was having..


No smoke, rough idle.. Would have to be running lean then.. Just need to find out why.. Maybe a clogged fuel filter? or injector? Best of luck on your search for the issue.. I know the pain of finding the gremlin..

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