Hello friends.
I've owned my 93 coupe since 2000. 112,000 miles. I should know all the tricks by now. I don't. During the early years it put me through a lot of grief with the opti. I know at least 5 or 6 in pretty rapid succession. Finally, I carried it to the local Chevrolet dealer. They had some good mechanics. All was good in the world. I would guess its been 5 or 6 years since I had any problems. Last Saturday was a pretty day. I took the top out, and drove down to the next town. About 50 miles. It was running well. A hot day. On the way back, it quit. I had to get it towed home. No fire at the plugs. No fire at the coil. I bought a new ICM from ebay. I tried another coil I had. No help. That Chevrolet dealer was sold, and the new folks don't work on old Corvettes. The good mechanic died. I see no codes. The last time I changed the oil, I noticed some leakage. Not enough to drip on the garage floor, but enough where blow back a little. It seemed so tragic, I always kept that engine clean! I can't see exactly where the leak is, only that it is the front of the engine. I hope the opti is just dirty and can be cleaned up. The last time this happened, I got Brad Errington to repair it. He tells me that those sensors are no longer available. What do you guys do now for opti replacement?
Any thoughts, ideas, or suggestions?
The coil I found was a MSD. It doesn't fit on my mounting bracket. Is there an adaptor? It is a 8226. I tested without bolting it in.
The ICM bolts to the front of the right head. That is a heat source. Seems like another bad idea.
Thanks

 

Sorry it's giving you trouble! No fun when good new parts are hard to find for good old cars! My opti died in that same fashion. It was heat dependent tho. Dead cold it would start & run till it got up around 100* coolant temp, then die. I didn't trust it!
Gotta keep a keen ear open to listen for it 👂 If it will run for a bit even, when it cuts off, listen if the fuel pump re-primes with the key still on. Sounds just like at initial key on. If it does prime right after it cuts off (on its own, nothing you do) then its something else, Fuel or ICM/ Coil. If it does NOT prime itself, it is most likely the opti. If the opti signal dies, it cuts fuel delivery along with it. Supposedly for fire 🔥 prevention 👍🏻 Just an easier check to do if the car will still start at all. **If that opti you currently have contains the Mitsubishi sensors, Don't trash it ** Petris is what i replaced mine with this year. Good luck with it!
https://petrisenterprises.com/blogs/...roubleshooting

http://shbox.com/1/4th_gen_tech2.html#opti_test
Great walk thru procedure for testing opti & ignition.

 

There's a bit in that Petris link about 92-93 ecm's doing stuff similar to opti failure. Idk the details on those, but maybe worth digging into 👍🏻

 

I failed to mention that I sprayed some starter in a can (either) down the throttle body. It still would not catch. In my mind, that eliminated, or at least reduced the chance of a fuel delivery problem. That could be wrong. I have a fuel pressure gauge I bough a while back just for this car. Maybe it is time to use it again. It is good info in your post. I will go back and check if the fuel pump comes on again.

 

If you sprayed starter fluid and it didn't attempt to fire, that would more likely indicate an ignition problem, over fueling. You provided the 'fuel' with the spray can 😉👍🏻
If the fuel pump is still working at all, it'll still prime at initial key-on. The reference i gave was if the engine is running and stalls out, does it then automatically prime again without touching the key, still in the On position? Either way, sounds more ignition related at this point.
If your handy/ comfortable with voltmeter, the workthru's in the links I gave help you narrow down what's happening with it. Good luck with it 👍🏻

 

I came to the same conclusion.
I have had the experience in the past. Years ago. It would be hard to start, but would finally would. I am thinking maybe 3 cycles of this. Each time progressively harder to start.. Then finally, it wouldn't start. This is Not what I am experiencing now. No warning. No hard start. It just quit while I was driving down the road at hiway speed. Spinning over but no start. My tester shows no fire at the plug, nor at the distributor. Even with a new ICM module.

 

ICM's can be bad right out of the box. Not sure about your coil setup? The testing procedure in the f-body link will show you if each of those parts are receiving correct voltage signal, and if they're functioning as a result. FSM certainly guides thru this as well. I only provided the link for those w/o a service manual. Gotta do some Tests! Or make a pricey$ guess. 🫤