Thread: Please help having trouble with 04 GTP

I have a 2004 Grand Prix GTP. I'll try and make this short. Got the car with water in the oil. It wasn't a head-gasket issue, it was a intake issue. Anyway had the heads off already pressure tested then milled the head and replaced the head-gasket and car ran fine then started spit and sputtering when getting into it. Engine light came on and said catalytic converter was bad so I replaced that and my buddy test drove and it was fine. I stopped by test drove and it was fine but couldn't take the car so I had my wife drop me off and on the way home I punched it and spit and sputtering again. Here is my question. The car obviously is an OBDII and I was wondering I know my Lexus has a 3 cycle computer and if it you reset the computer it runs great. Now seeing that I was the third cycle person to drive the car is when it messed up It says random misfire so what might this be? If it were a plug or a part it would still be messed up whether the computer has went through the cycles or not. It just runs rough after it goes through cycles. Could it maybe be the gas in it as its about 3 months old from where it sat. Sorry also trying to write this with pain meds from a tooth procedure lol so hopefully it makes some sense. Thanks

Yes plugs have been changed and it just says random misfire and yes they have been gapped as well. And thats what I am saying if the plugs or any other part was the issue it wouldn't need to to run through the cycles, it would run rough on the start up. I was just hoping a tech would see this and tell me if the gas was bad if it would run right until the computer noticed it if that was even a possibility. And I haven't been around the car so thats why I haven't filled it up and drove it just curious as its driving me crazy. Thanks for the reply as well.

Originally Posted by Fivefingerdeathpunch

So what cylinders are the misfires coming from?

Have you replaced the plugs yet?

Yes. But my question IS could the car be running fine and the computer detect the gas after it runs through all the cycles. All simple things have been done I obviously know to chack the plugs and what not I am beyond that point just doesn't make sense it does this after the drive cycles.

I agree with dsmuts. Do a compression test. Misfires are commonly plugs/wires/coil or gasket.

Are there any GM techs at this forum site that I could hit up. All of those, wires, coils ect. would have issues on start up. I went home last night reset the computer and it drove great again. Plugs and wires are fine, and coils are being tested today but I already know thats not gonna make a difference as I have driven cars with bad coild and doesn't matter if you reset the computer or not still runs like ass from the get go.

Don't dismiss the coil packs or wires yet. It's not unusual for the temperature or weather to effect either. Humidity and moisture can expose bad wires or coils that might not be seen on a dry day. But you're right that resetting the computer wouldn't change that. It would just be a coincidence.
Resetting the computer would cause a relearn of the throttle position and transmission shifting. Maybe the misfire was the TPS choking just a little too much air? I believe the reset would also clear stored data like the knock sensor. If the knock sensor was bad and telling the computer to change the timing, maybe that could cause a misfire.

Anyone want to buy an 04 Grand Prix GTP with now 74,000 miles. I'm done I am going back to my easy fix Japanese cars, lol. But I am serious I am done with it and don't wanna pay another person to diagnose the car and me nickel and dime myself like I did on my last american car. I guess I will post in the classified later today.

Will be foresale today so please call me if you are interested. Thanks