I just want some more opinions here. I have 94, M6 that was running great untill yesterday. It suddenly decided not to run right. It cranks and starts but runs on like 3 cylinders. I checked fuel pressure and had 41 PSI on prime and the same while it was trying to run. I scanned it with a Snap-On scanner and there are no codes stored although the line that says " OK to run" just had ** instead of yes or no. All other data looked good. I pulled the #2 plug wire and observed spark but it looked erratic. I also checked injector pulse with a noid light and it showed ok. I'm pretty sure it's the opti but I want to be real sure. Any other ideas?

 

Sounds like that might be it.If you buy a new one get a Delco.Some of the Auto Zone stuff is not right. If YOU change it handle it carefully taking it off and look at the back of the old one and set the hole/slot on the new one like the old one. Don't force it together the drive pin has to go in the hole/slot to work properly and don't over tighten the mounting screws/bolts.Mark your plug wires before removal with some masking tape and a pen-- then remove tape after you are sure it is right-- opti has plug # marked on it.Just put right top-R2 R3 R4 ect.

Go to Shoebox's site for more details.

 

Good tips. Thanks a bunch.

 

I would check the spark coming out of the coil as well as the opti end of the coil wire