My 1993 Coupe has 110k now. Anyone who has read my previous post here knows I have had ongoing opti problems. At least that’s what evidence is leading me to, but I am rethinking this. The typical scenario goes like this. The car won’t start up. No fire at the plugs. I replace the opti, and it runs for a little while. 50-500 miles, and quits again. At some point I gave up doing the same thing over and over, but wishing for different results. I started taking it to the local Chevy dealer. I had some better results. At least for awhile. This was the 500 miles of service time frame. Then the corvette mechanic died of cancer. The last time or 2 I have used the opti doctor to rebuild one of the last Delphi units built before they went under. The last time the unit was pulled off, sent back to the opti doctor who reported the unit was fine. No problems. Put it back on, and it ran great again. For a little while. It’s getting hard to start now, but runs fine after I get it started, and cranks again fine once warmed up. New things I’ve noticed this time, is the idle seems to pulse up and down slightly when it idles. More concerning, it seems to run hotter, especially on a warm day. Did the Chevy dealer go back to the factory spec thermostat? I should ask. The cooling fan comes on at random times. When I first crank up and things have not yet warmed up, the fan comes on. Other times when it is supposed to come on, it does not. So what is in common with these problems? I suspect the ECM. I had it rebuilt once years ago, and have replaced every ignition part that I know of multiple times. New plugs, wires, ICM, and the opti. Any ideas? I am running out of options as the car ages and parts become harder to find. I am thinking about sending the EMC in for repair because, as I understand it controls many functions. It couldn’t hurt. I am looking at SIA, but would welcome comments from fellow LT1 era C4’s about how you solved a similar issue.

Thanks in advance for your help.