rockfangd Posted July 17, 2012 Report Share Posted July 17, 2012 Hi all, one of my coworkers has a 2004 Pontiac grand prix GTP supercharged. It has bad misfiring especially on acceleration. At idle the SES light is on and on acceleration it is flashing. Only code stored is P0300. For multiple cylinder misfire. He has had plugs, wires, and all 3 coils changed. Everything seemed to improve the problem slightly but nothing cured it. I told him to try chevron Techron for a few tanks and it did no help. He also replaced the fuel filter with no luck. I have 2 concerns as to what may be causing the ptoblem. #1 the sleeves on the plug wire ends. They are steel and go on the wire at the plug end. I was wondering if they could be causing arcing to ground. #2 I was thinking maybe the ICM might be bad. But I dont want him to throw parts at it hoping it works. I think it also throws a catayst efficiency code. Probably due to the raw wasted fuel from the misfires. Also throws a lean bank 1 sometimes. hope all this info helps. If I had more physical time with thee car I could probably figure it out but being so busy I just dont have the time to get too far into it. thanks all Quote Link to comment Share on other sites More sharing options...
AL Posted July 17, 2012 Report Share Posted July 17, 2012 Pull the spark plug heat shields off, Ive seen tons of misfires because of them Quote Link to comment Share on other sites More sharing options...
rockfangd Posted July 17, 2012 Author Report Share Posted July 17, 2012 Thats what I was thinking. I see it alot. but I am just not sure as to why they are there. I have never had problems before when I have removed them. I just worry about the risk of fire. It had oil leak when he bought it from both valve covers and was burning on the manifolds. I preached to him to get it fixed due to the risk of fire. I see too many GMs in the junkyard that had engine fires Quote Link to comment Share on other sites More sharing options...
cubsfan24 Posted July 18, 2012 Report Share Posted July 18, 2012 My brothers 08 GP had a p0300. Although in his case cylinders 2&5 were constantly misfiring even at idle. The second coil location had no spark despite swapping coils around. I had previously removed the heat shields from around the spark plugs. Got a used ICM from the junk yard and that fixed it. Even though your problem sounds a little different, my brothers car had a vibration on the highway only on acceleration for a while now with no codes. The new icm solved this too. Quote Link to comment Share on other sites More sharing options...
rockfangd Posted July 18, 2012 Author Report Share Posted July 18, 2012 well today I removed 5 out of 6 of the sleeves. I cant get the wire off the plug near the power steering pump. I tried like heck and gave up for today. Most of the sleeves were slid down to the plugs and looked terrible. When the new plug wires were installed in may the mechanic didnt use the dielectric and they were extremely tight. I will have to see how it did when I see him tomorrow. Still not sure what the purpose of the shields are but I dont really have a better solution other than using oem plug wires rather than aftermarket Quote Link to comment Share on other sites More sharing options...
rockfangd Posted July 24, 2012 Author Report Share Posted July 24, 2012 Ok to update this The #3 injector was replaced and light has not come back. not quite sure why It would throw a P0300 and not more specific but it is possible Quote Link to comment Share on other sites More sharing options...
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