I hav an '04 grand prix gt1 w/227k miles. It was missing badly wen i bought it. Th guy told me it was most likely a coil pack...and it was. I put a new 1 on & it ran rite 4 awhile.
Soon after i put tht coil on it started missin wen i'd giv it mild 2 heavy acceleration. So, i replaced th other 2 coil packs with a couple tht i had tht came off another gm v6 i had layin around in my garage tht came off a 3.4 v6....i was told they'd work on th g.p. So i put em on.
It ran like a raped ape 4 a few days then it started missin again wen i'd accelerate, but not quite as bad as b4. I put new wires on with no change. I did put a new plug on #6 coz it was also givin a misfire code on #6.
I jst put 2 new in th box coil packs on & th engine lite jst came on. It now has oxygen sensor codes as well as a rear wheel sensor code.
It shuld b mentioned tht th car has dash lites on 4 th traction control, th abs lite, and 2 or 3 mor......ben on since i bought it.