a friend of mine's stock 94 m6 z28 was doing the whole misfire thing, so i replaced the opti, coil, and icm for him.

the car is stock with a K&N CAI and flowmaster catback

BEFORE: misfire while driving, hesitation under load, black smoke, sell of unburnt fuel etc. however it was idling funny when warmed up. if we started the car cold, it sounded great until it warmed up. we decided the opti was a good place to start, since it was a 130,000 mile car. turns out the distributor was full of rust, so it wasnt a bad idea.
the first thing it would do when it hit temp was jump to 2000-2200 rpm. after a few seconds there, it would drop to 500rpm. after doing this a few times the car would sputter and shut off, with a backfire or two.

NOW: The misfire, hesitation and smell is gone, but the idle problem is not. ses is on, but i have no scanner(yet). Did a few searches on the topic on here, but came up short.

Any help is much appreciated

 

Checking for codes is the first thing I would do. Free at most auto parts stores.

 

Don't most parts store just carry the OBDII code reader?

 

I remember before I got the datalog and could do it using the lap top that one said they would not replace the old unit once it went bad. Very possible that because of the age of our cars they are getting harder and harder to find. Calling would be a good idea.

 

None of my local parts stores have them. But the datamaster is free on me laptop....well for a little while longer.