I've got a '94 Formula, M6, the usual bolt-ons, shorty headers, madtuner PCM, stock internally. it just decided to start randomly dropping cylinders, popping out the exhaust, not enough power to pull itself up the driveway, things of this nature a few days ago. It only does it after running for a good 20 minutes or better, well after it has hit operating temp, so it seems to take some heat soaking to bring the problem on. I have never put an opti in it in the 80k miles I have owned it, so of course i am suspecting that first, but i will check the ICM and coil tonight before i tear it down. my concern is, i noticed last night that there is a tiny coolant seepage coming from between the head and block on the front of the head, passenger side, but I do not see how this is causing what I am experiencing. any thoughts on this? thanks

 

sounds like your opti is going, mine did the same thing, i bought one of the cheap black cap optis and it worked till i could buy a delco, just swap it out,

i have a 95-97 opti, if im thinking right you might be able to swap out the optical sensor, rotor and cap, 50$ shipped

 

How well does it run when its cold? If it runs real good for a while, you might have an easy fix. There are a few things that might cause it to only run bad once warmed up. Have you scanned it for codes? Some won't trigger the check engine light.

 

Try disconnecting one of the O2s and see how it runs once it's warmed up. If no problem then, you know it's a control problem while in closed loop since disconnecting an O2 forces it into open loop all the time.

If that does NOT make any difference, the next time the engine is dead cold. Start it only long enough to see that it's idling ok then shut it down quickly to not heat any components that you will now test. Now using a blow dryer, warm one item you suspect might be a problem at one time. Heat it just to the point of being hot to the touch, like the ICM, then start it long enough to see if it is acting up or not and then shut it down quick.

If it didn't cause it to run rough when tested, move to the next item, like say the opti, position the blow dryer so it warms only the opti. Then test again. Keep moving along to the next item in the chain until you find one.

You can also do a few other things. Look at the engine while it's running at night in absolute darkness to see if there is any sparking.

Pull the coil and look for tell tale white dots on the insulator body indicating you had what I call "side firing" where it arcs to the metal laminations.

Incidentally the coil is considered a tune up item and should be replaced periodically.

One other thing you can do is pull the plugs to look for signs of misfiring.

This is purely FYI.
My Vortec truck once had a no start problem. My "mechanic" friend, and I use the term mechanic wrong. Convinced me I had a fuel problem. So after a couple of hours of changing out the FPR. (bitch in a Vortec). Same problem. Once I removed the plugs I saw 3 on one bank were black and the 4th was perfect. At that point I knew it was ignition and knew the only thing it could be was the cap and rotor. Viola. Fixed.

Oh yeah, one last thing. The plug wires where they go around the corner of the block behind the alternator are very tightly pinched(for lack of a better term) against the block. It wouldn't surprise me if they were firing to the block instead of the plug.

Look for dead cylinders to start looking in the direction of the ignition components on that cylinder.

 

I appreciate all the responses and help. I tore it down, the opti will not even spin right, it binds and sounds like bad rough bearings, etc. so now my question is, what is the difference in Delphi CZ20009 VS ACDelco 10457702, are these the exact same thing? thanks.

 

Yes based on the pictures they are the same.