04 GTP WOT Misfire

**JHGTP** · 02-23-2012

Hey everyone, It's been quite some time since I've been on here but I have an issue that I've found too many "possible" solutions for and a very small budget. Recently my '04 GTP has been running really hot and I have a misfire condition at WOT which somtimes sets a P0300 code but after "Driving Mrs. Daisy" the code clears itself. I thought this may be the coolant for the running hot issue and noticed my coolant was low so I topped it off with Dex-Cool and it seems to run a little cooler but still running hotter than it used to. And like I said I have found too many "possible" solutions for the misfire condition such as burned/plugged CAT, clogged injectors, Coils, etc. Is there anything any of you can suggest that I could try?

**dsmuts** · 02-23-2012

when did you last change the plugs and wires? Where is your coolant going? Lim leaking possibly.

**boostedcompg** · 02-23-2012

how old are the plugs and wires? do you have a way to scan? mod list? we need details

**JHGTP** · 02-25-2012

Originally Posted by boostedcompg

how old are the plugs and wires? do you have a way to scan? mod list? we need details

Yeah sorry... she's got 148k miles on her and as far as mods goes all I've done to her is replaced the Resonator with a straight pipe (had that done when I had a new CAT installed due to a P0303 cylinder 3 misfire; broken spark plug my now ex-wife failed to figure out while I was overseas), MSD coils, MSD wires and NGK copper plugs March 2010 and a new OEM starter and battery late 2010, and 3 weeks ago an OEM EGR Valve and gasket. Everything else is stock. As far as where the coolant is going I have no clue, there is no leaks underneath aside from a minor oil leak from what I assume is the front main seal. My father-in-law thinks the head gasket is faulty in which case I'd be burning the coolant but I don't smell anything other than the typical exhaust fumes and no unusual smoke from the pipes, and aside from that I have no idea. All this started when I moved from Northern Cali to the mountains in Southern Cali and my stock EGR Valve failed due to too much carbon build-up. Cleaning did nothing so I replaced it and that fixed the problem completely. But now I have a choking or misfiring at close to WOT and wide open throttle. Also, while the EGR was faulty I had to drive around with this condition for a few weeks due to lake of funds and the temp gauge would always be close to red when I stopped, idled, or got caught in traffic, but would be normal temp while driving normally on the freeways. Now that I have the new EGR valve in and added Dex-Cool coolant the temp gauge still runs high but not as high as before. I really don't want to find out the CAT is burned again cuz it was roughly $480 for the one I already had installed.

Oh and as far as scanning goes, I do not currently have a scanner but looking into getting one for the history codes and Freeze-Frames to find out what was going on when the codes were set assuming they haven't been cleared by the PCM by now. And I currently have no codes or MIL light on.

P.S. Sorry for my speech....I write a lot for a living :-P

**JHGTP** · 02-25-2012

Originally Posted by dsmuts

when did you last change the plugs and wires? Where is your coolant going? Lim leaking possibly.

What's LIM stand for btw??

**Fivefingerdeathpunch** · 02-25-2012

LIM = lower intake manifold.

Throw those MSD coils and wires in the garbage, those always cause a misfire problem on these cars.

Switch back to stock coils and wires.

**AjL227** · 02-25-2012

Usually, when I see WOT misfire I'm thinking spark blow out. Gap the plugs @ .055"
Cheapest option would be replacing spark plugs, and using oem coils and wires. MSD makes good distributors, not coils.

**dsmuts** · 02-25-2012

If your loosing coolant your lower intake manifold gasket is leaking. It's pretty easy to change out, flush your coolant at the same time because you likely have a bunch of junk in your coolant causing it to run hotter.

**JHGTP** · 02-27-2012

THank you all for your input, I'll see about getting some coils and wires. The reason I have MSD is one of the original coils failed to produce power (my stupidity, long story dont ask, lol). Which do you guys recommend would be the best brand option? And thank you for the coolant advice, I'll look into changing out the LIM gasket. Thank you all again for your help, I'll post again with results as soon as I have them.

**Bio248** · 02-27-2012

best brand of coil packs are the stock ones. get some replacements at your local parts store or try and score a clean set at the junk yard.

**blueguy** · 02-27-2012

Originally Posted by Fivefingerdeathpunch

LIM = lower intake manifold.

Throw those MSD coils and wires in the garbage, those always cause a misfire problem on these cars.

Switch back to stock coils and wires.

Coils yes, wires no.

I've had my wires off a trillion times and on multiple cars to figure out misfire issues...they've got nearly 60k on them. Great wires, especially with the bendable boots.

**boostedcompg** · 02-27-2012

When changin your lim don't put dex cool back in it. Go green. And I have stock coil packs if you are in need...but they are cheap at the autparts store as well. Let us know.

**JHGTP** · 02-28-2012

Originally Posted by boostedcompg

When changin your lim don't put dex cool back in it. Go green. And I have stock coil packs if you are in need...but they are cheap at the autparts store as well. Let us know.

Go Green... I have heard and noticed that the Orange Dex-Cool turns muddy and has caked the inside of my my reservoir bottle. Could that also mean that the Radiator, hoses, or even the water pump and jackets inside the block are gunked up as well? I've had a concern about this for quite some time but thought that since the manual and the dealership recommends Dex-Cool Orange it's supposed to happen and wont really harm anything. I had 2 radiator flushes done back-to-back 2 years ago cuz it got so bad but I've always had orange put back in.

To give some more background info, my ex-wife tore up my poor baby while I was overseas fighting for the wonderful USA and I know for a fact all these issues are because of her negligence. Racing and sliding through dirt roads, street racing, etc.

**Bio248** · 02-28-2012

even most off the shef 'green' coolants are the same forumla as the dex. color means nothing. dex will not perform poorly so long as the cooling system is maintained. dex mainly gunks up when it is exposed to air, IE a leak.

**boostedcompg** · 02-29-2012

I have never had green collant turn to mud. Regardless of air contact. Having said that I flush mine once a year and replace. But I did that with my 05 sierra as well still using dex and it still turned to mud. Dex cool is evil.

**SlowNA06** · 02-29-2012

Needs new spark plugs and GM coils.

**JHGTP** · 03-01-2012

So, Coolant flush with standard green coolant, and stock coils w/ new, Irridium(?), plugs...got it. And you guys mentioned Dex-Cool turning to mud once exposed to air. This, I'm thinking, could be signs of a leak since I have also noticed the coolant level low from time to time despite the fact that there is no trace of a leak on the ground. So, more than likely I'll need a new LIM gasket as well? And I also want to add, thank you all for your help. I'm really fortunate to have people out there like you all that love Grand Prixs as much as I do and hate to see them go down without a fighting chance.