Thread: GTP random misfire/hesitation

Ok, I'm new to GPF so don't bash me too hard.
I've got a 2002GTP with minor mods (3"DP no cat., MSD coils, MSD 8.5mm wires, and AC Delco Irridium plugs, along with a CAI) Recently I had a bad misfire under heavy acceleration, around 3-4k RPM. It would only miss a few times, then accelerate like normal, so I went and replaced the plugs (which had marks on the outside porcelain) with Autolite 104's. The car wouldnt Idle at all, and didnt want to run. So i put the old plugs back in, and it ran Perfectly, no misfire at all or anything.

Then later that day, I went to pass a truck (50-75) and i got a horrible hesitation/misfire. The car bogged horribly, and felt like it was starved for fuel.

Replaced the fuel filter, and checked the pressure at the rail, 50psi.
Checked vacuum, pulling about 20psi.

Any idea what it could be??

Yeah, i still have the stock coils, but the weird thing is, now its just stuttering really bad under about 90% load, or more. But no misfire, and no SES light.

ignition module maybe? also, do not run platinum or iridium in boosted cars, they run hot, you want coppers.

Sounds like the same problem i had with my MSD coils. Id punch it and it would hesitate for a moment. I switched back to my stockers and that problem went away. I like the way the msd coils look but they are a demod imo.

I have a 2002 pontiac Grand Prix GPT about 64000 miles on it and about every time you get on it it starts to miss the 1ST time replaced a coil pack and it seemed to be fine the 2ND time i replaced plugs and wires and it seemed to be fine again the 3RD time i replaced the same coil pack witch is the middle pack that is cylinder 3 - 6 but this time It still missing also it has been hooked up to a tester and it has a code of p303 or po303 need to find out what is the real problem???? Could it be a plugged injector ??? The car also has no catalac converter

its from not having a cat, had the same problem when I installed my headers and got rid of the cat and started getting the random misfires. The first thing I did was change the spark plugs but it didnt help what so ever. I installed a high flow cat and random misfires stopped =]

I am having this problem and sometimes my car wont start how Where should I look for sparks at? by the coils or somewhere else?

check your coils with an ohm meter, and have autozone test your ICM.