Mechanics

RANDOM MISSFIRE AND TRANSMISSION PROBLEM

Pontiac Grand Prix

1999 grand prix gtp with 145000 miles. It has 3.8L with a supercharger. About 40k miles ago I began having an intermittent cyclinder 3 missfire and rough idle. It would happen when the engine was cold or warm. It would be a very rough idle or very soft. It would go for days with no problem then I would have days where it felt like an earthquake. I took to the dealer and 1st they said induction service, then plugs and wires, then fuel injector #3 replacement. I fixed what they said and nothing worked. They told me my solenoids and compression were ok. I was too upset to go back there since. I've just learned to live with it for the past 2 years. Recently I've just had my transmission worked on under warranty repair from AAmco 9 months after they rebuilt it. After getting it back I'm still having problems. When I shift from R to D or vice versa it's very clunky and makes a noise. Also both wheels shake when I shift. This video is after I got it back http://www.youtube.com/watch?v=rVpTI4HkKIQ. After going back to Aamco they replaced my boost valve with an oem boost valve. I'm still having trouble which is http://www.youtube.com/watch?v=Hb0nU9BTy6o. Now Aamco says that the tranny is fine, that my problem is from my engine miss-fires. They say that my engine rpm is too high at 764rpm and that now my error code is p0300. Aamco did a scan and gave me the info that I included in the the picture file. They also say that my front right wheel bearing is bad. Also my valve rocker arm cover is leaking and I plan on replacing that. At 127k miles I had the MAF sensor replaced and the throttle body cleaned. Any ideas or advice about the missfires would be appreciated. Do you think my missfires could be causing the shifting problem? Thanks.
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Cavemand
August 27, 2007.



Sounds like they replaced everything but the coil pack. Did the codes actually tell them " misfire cyl 3" or was it random the whole time? P0300 is a random miss code not cyl specific. If compression is good and the plugs abd wires are new, all that is left is the remaining injectors and the coil pack. Yes, the engine running poorly can make the trans feel as though it isnt working properly

Tiny
Jack42
Aug 28, 2007.
Thank you for replying so quickly. Back in 2005 when the missfire started happening it showed p0303 which was specifically a cylinder 3 missfire. Recently it's only been coming up with the p0300 error. Once I get paid I'll go out and get some new coil packs and hope that works. I looked up the packs on Napa and they're about $30 each. They also had some others that were mid 50's. Will the $30 work just fine or should I get the more expensive ones? Or should I get the coils somewhere else. Thanks a lot for your help.

-Dave

Tiny
Cavemand
Aug 28, 2007.
I always recommend factory replacement parts, but do as the budget allows

Tiny
Jack42
Aug 29, 2007.