I need help because I'm very cofused about this. The engine starts and runs fine for about 5 minutes after that a "miss" (i think it's a miss) so then youll stop and when in drive it misses bad, idle drops to about 500rpm. then you go a little and it misses to about 1500 then it shoots up to 2500 and begins to miss agian. It only does this like 1/2 the times I drive it. Not sure if its the cold but the cold shouldnt make it miss. I think it could be ignition because a faint smell of gas comes in everyonce in a while. Also I figured a miss would trip the engine light but it hasnt. It also doesnt have the same sound and feels very very slugish as If running on like 6 cylinders If you can help off of the info I've given please do. Im really, really stumped

 

sounds like an old fashioned miss. suspect optispark, wires, plugs. im assuming your car is a 95 with your sig. and if thats the case it may not support the misfire monitor in the pcm. 96 up definately does. look under the timing cover for a crank sensor. you may not have 1. the crank sensor is responsible for misfire indications.

 

Wires are a common source for "misses". How many miles on your O2 sensors? The first couple of minutes the car doesn't use the O2 sensors and you said it runs fine...could be O2 related.

 

Thanks, I'll look in to the o2s although I think it may be the opti because the wires and plugs are fine in most aspects, I have about 5000 on the o2s I bought new ones when I put on the headers.