My buddy has a 95Z 6pseed, it has about 88,xxx on it. He's had it for a few months now. He put a set of 17x11 ZR1 rims on the back with the 315/35 nittos. We took it to the track the past two weekends in a row and after he heats the tires up and launches, under the heavy load the car misses starts sputttering and sometimes backfires. Driving around town its fine even under 2/3 throttle, but at WOT the car seems to go slower. First I thought opti or the coil, but we need to check the plugs too I guess. any suggestions?

 

i would guess the coil, but that is a guess. what i would do first is make sure the plugs are ok and all snug. also, make sure you good connections with the wires on the plugs and the coil. you could also check for arching at night.

 

Any other ideas? If it was the plugs or the wires wouldn't you feel the miss all the time? This just happens under load, like the ignition system can't keep up. I am about to put headers on this car, with new wires/plugs and want to get it fixed before hand so it wont mask the problem or make it worse.
Thanks

 

Not necessarily...its much harder for the engine to keep up under heavy loads. We had a 96 Monte Carlo come into our shop and he had a spark plug that was cracked. At idle, our scan tool showed no misses at all, but once you put a heavy load on it, the misses started rolling in. If it were my car, I would do a basic tuneup on it (plugs and wires) and then worry about it after the tuneup. If it still does it, it is pretty much narrowed down to the ignition coil or the optispark.

 

I have the same problem. Here are a few things you'd wanna check.

coil
ICM
plugs
wires
opti
injectors
fuel pressure
MAF