Thread: 04 Grand Prix GTP Power Loss Problems

Ok I have a 2004 grand Prix GTP that I've been having a few problems with we've had it maybe 3 months and the first couple of weeks it ran fine, well it started acting like it needed a plug change, it's my sister's car so she just kept on driving it and needless to say the car went from pretty much the same power but a faint stutter going uphill on the interstate (no CEL at this point) well the car has now gotten to the point to where it cranks fine but when it starts up you usually have to give it some gas to stay running but only at startup, well the car has completely awful power, a bit better than about a month ago but still bad it had gotten so bad that when you would floor it from a dead stop it would barely take off while going ba ba ba ba ba continuously (literally like only 2 or 3 cylinders were firing) so we changed the plugs, saw sparks from the wires so replaced those too, we've checked the posts for the coils and the coils themselves all fine, the engine sounds like it's still misfiring or something especially under hard acceleration and it makes the supercharger make a loud twittering noise instead of its usual whine, the car always tries to get hot too at first it was perfect bit now even in 55° weather you have to run the heat on at least low if you sit still for say 10 minutes or longer, another thing that's really weird is that the car runs absolutely perfect when it's very first cranked and is completely cold, motor runs strong it'll sling you around if you let it and the supercharger whines like normal, but as soon as that temp gauge starts moving up the power fades away more and more, sorry if this is jumbled or drawn out I'm not the best at wording things can anyone please help me on this!! Also the CEL has been on awhile now it's constantly on and starts flashing every now and then, but for some reason my OBD scanner keeps crashing at the exact same "percent" everytime I try to read the codes, so I've yet to be able to do the simple read the code and diagnose it, thanks for anyone's help by the way!!!!

Flashing CEL usually means a random multiple misfire.
Have you cleaned the throttle body yet? If not that should help the need to give it gas at start up to help it idle.
As far as the coils, how did you diagnose them?
When the cars running take a water bottle and spray each coil at a time and take notice if that makes the idle stumble. If it does after spraying a coil then that coil needs replacing.
I would even take your Ignition module in to have it tested to. That is the electronic board that sits below the coil packs. That can fail to.
When's the last time the supercharger oil has been changed?
Hopefully the engine just needs some routine maintenance done to make it run awesome again.

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We used the Ohm method on the coils I'll definitely try the water bottle method thanks for that I've never heard of that and we have 2 different scan tools they both work on other cars but not this one for some weird reason, also on the SC oil I'm not sure honestly we haven't changed it and we've had it a few months now the guy we got it from didn't mention changing it when is it supposed to be replaced and thanks again I'll try the TB cleaning too

OK thanks for the warnings I cleaned the upper intake on my Honda awhile back and got it all back together to find out that i got engine degreaser in the idle air control valve I wasn't happy with its idle to say the least and had to redo everything so it pays to be cautious I'll also check the ground point i didn't even know about that plus I never have looked at the PCM thanks everybody!!!

I'll try that as well I've actually wondered about the CAT alot but it's hard to just guess on things to tinker with since it's our only ride at the moment that's why I'm glad I can have all of y'all's opinions it's a huge help really, I'll definitely try that as well though thanks, the ba ba ba at WOT takeoff actually stopped after we did the plugs and wires but I can hear the engine and it still sounds wrong it always has a smooth more 4 cylinder like sound (perhaps not the best example?) when it's running right but now it's more of a V8 engine noise along with the fluttering supercharger sound, but only when it starts to warm up is really weird, numerous online searches also have me worried about a clogged fuel filter or a weak fuel pump hopefully not though

Again thank you to everybody for your responses I posted on several Honda forums when I had a continuous misfire with an F23 accord I had and I always either had no responses or people would only state the obvious like plugs but it actually turned out to be the egr port was clogged and the big thing the valves were too tight. Smooth as butter now after I get rid of it wouldn't you know lol

And btw I know it's a V6 but I have a Sonata 3.3 (disabled ATM) that has a very good V6 sound and this Grand Prix has never really sounded like that I guess because it torques up so fast it flew when it was running right and still does early in the morning for the first maybe 5 minutes but I'd like that all the time of course lol

Yeah Its not a very "sporty" sound lol I see people with straight pipes on them on YouTube I'm just like well glad you like it that's not for me though not on a 3.8 lol