98 gtp misfire need help:(

[mskram1]

Ok so ive been fighting with my 98 gtp for about 2 months now. ive crawled this forum and realized that a lot of people have my same problem but ive changed every part that they've suggested (except my coils but i have spark) and im still stuck... it seems that it is misfiring on almost all cylinders from 2500rpm and above and if i hold it at anything above that for more than 20 seconds i get the blinky ses light. but anything below 2500rpm it runs fine. the only mods i have are a 180* thermostat, brand new autolite 104's, lim and sc to manifold gaskets as of yesterday, my icm tested good, new vacuum lines and rubber t's, new cps, and a short ram intake. any help on this issue would be greatly appreciated.

[shawngtp]

clogged cat, bad MAF? My MAF was going bad and was causing all kinds of weird things to happen.

[gtpinsc]

why do u have 104's in ur car?

[RideMr2]

I suspect the cat too.

How many miles? What codes are you getting?

[gtpinsc]

im guessing hes stock.... if so 104's arent helping the problem at all.

[mskram1]

Its throwing the p0300 code... and I was under the impression that the autolite 104's were a cooler plug and would help fight knock... no clogged cat because there isn't one(forgot to mention that before) kinda starting to think its my 02 sensors its sayin low voltage on bank one and no signal on bank 2 on my elm327 scanner... and 178,000 miles

[Poil336]

i'm saying spark plugs. 104's are a heat range cooler, but with a stock car, temps should be kept constant. knock wouldn't be a big enough problem unless it's f*cking boiling out. put 606's in and it might fix your problem. other than that, it could be the O2 sensor readings, the computer might trying to be compensating based on flawed readings

[machinegunsquid]

Its more than likely the plugs. When I put my 104's in on a near stock motor, it misfired like all hell. But when I put my stockers back in, not a single misfire.

[gtpinsc]

injector takin a **** maybe?
104's should be used in 3.4 ish pulley applications. i ran 605's on stock pulley copper of course.

[machinegunsquid]

I doubt the injectors would, maybe low-grade gas along with 104's...that'd be fun

[DBGP]

had the same issue. took my gp to the shop and it ended up being a bad rear o2 sensor

[mskram1]

Well its parked in the garage havin to drive my 2000 gp se untill I can fix the problem...it was misfiring before I put the 104's in but i'm definately taking those out when I can afford new o2 sensors... and as for injectors they all tested fine... gonna get a zzp downtube with cat when I get a job thanks for all your suggestions

[mskram1]

problem solved... bad o2 sensors, 3 bad coil packs and a failing icm... $800 including labor

[offroadfury6]

careful 104's in a stock engine could shred ur cat ( ask me how I know ).
but i've got this issue as well

http://www.grandprixforums.net/servi...oon-41762.html

gonna check coil's next I guess.