This is the first time i've noticed it, probably because I haven't driven the car that much this year. Seems to only happen after i've driven the car for about an hour, I know sounds weird. It'll seem to cough or stumble during acceleration, or even if i'm just cruising. Got so bad friday that when I just floored it, it was bucking and fartin and everything, terrible. But then like bout hour and a half later, started it up and it ran fine. Obviously first thing I thought was Opti, but anyone got other ideas? Coil on the way out maybe? I don't know what would make it do this only after driving for awhile.

 

Come on, someone take a stab..

 

Have you checked the fuel pressure during the problem. Tape a fuel pressure gage to the windshield. Sounds like a heat soaking problem. Could be ignition as you said. Another thing you can do when the problem occurs, check each plug wire with an inductive timing light to see how they are firing. If one is missing bad enough you might see it with the light.

 

The heat soaking isn't a bad idea, the #1 or 3 primary comes almost in contact with the fuel lines on drivers side. Its always worried me and I actually put a piece of sheet steel between it. How could I tell if the fuel is getting too hot? And why would that make the car buck and fart?

 

I had the same problem and i the first thing i immediately thought was that it was a heat soaking problem. I have a new opti, plugs and wires so i just took a stab at what was still original. I replaced the coil and now everything seems to be running great. I guess it is really common for the coils on these cars to get heat soaked easily when they start getting up in the 75,000+ mile range...escpecially with headers!!

trav