JM95

I had an occasional misses at operational Temp, no codes set. This has progressed to the point where th engine shuts off instantly, it sometimes restarts it self (manual Xmission) or I can push in the clutch and restart with starter. I can duplicate this in the drive way at full op temp 198 to 203 F. Here with a Leslie Spark detector in the coil wire to Optispark, I can crank imediately but will have no ignition (coil output) for 10 to 15 seconds. When ignition HiVoltage appears the engine starts perfectly and runs smoothly at idle (900 rpm) and none of the Optispark symptoms. Optispark replaced Oct 2010, along with WP, spark plugs and wires. Temperature on Ignition Coil Module and coil is in the low end of operating temp, 198 F taken with remote reading Pyrometer. Changed out Borg-Warner ICM for OEM AC Delco, car ran at idle and at 200 F for an hour and a half. Must be ICM, then with OEM the engine shut down while idling in traffic (temp 202 F). I have ordered new AC Delco Coil. I don't think its the Optispark as no typical symptons and the car runs strong under aggressive driving when it runs. Car is 1995 LT-1, (stock P engine), coupe, ZF transmission. Ran diagnostics again, no codes. Fuel pressure 42psi. Noid on injectors looks normal. Cleaned all grounds and positive connection points before distribution to fuse blocks. Any thoughts?

DMarusa

Joe, How did you resolve this problem. I have a very similar problem.

I bought a Chandler Motorsport distributor in Mid-December and installed it over the Christmas holidays. At the same time, I replaced the water pump, O2 sensors, fuel injectors, wires, plugs, and coil. The car has run fine for the last two weeks driving up to three hours a day, but I've developed a problem in the last few days. The car runs fine for 15-20 minutes and then shuts downs, even while driving at highway speeds. The engine is not overheating. It will not restart for 10-15 minutes. When it does restart, it starts right up and runs perfectly. Each time this has happened, I've driven straight home without a problem.

Because I suspected this was an ICM issue, I replaced the ICM yesterday, but the problem remains. I have found countless forum threads where people have very similar issues only to find the problem being the optispark. I really don't want to pull the Opti again since this is my daily driver and I'd rather eliminate all other possiblities first.

When I replaced the ICM, I noticed there was no thermal grease... or it had been washed away over time. I bought some Artic Silver from Radio Shack and used it liberally. Do you think the old ICM overheating could have damaged the new coil? Ive never heard of a coil intermitantly failing. They either act up causing the engine to stumble, or fail completely.

Thoughts????

JM95

I doubt if its the Optispark. I also run a CHS Optispark so far so good. HOWEVER, the most likely failure in the CHS is thermal failure of the electronics. I would start with an inspection of the coil wire and its connection with the Optispark and the coil. I had a heat failure in the coil wire at the coil. The clip had come loose from the center conductor and when it got hot they separated. Thermal failure of the coil itself is not unheard of. I would bet on the problem being electrical in the area of the ICM, coil or Optispark. LT-1s just dye from problems here as oppose to random misses from electrical problems else where.

sailorsteve

It is not unheard of for a coil to have an internal short that shows up intermittently when hot.

DMarusa

I stripped back the wiring harness from the ICM and coil all the way to the rear of the engine along the fuel rails hoping to find a short and I discovered that a previous owner had apparently replaced the tach filter. The splicing was done with those crimp connectors frequently used to connect trailers lights. The ground wire to the filter was also very mangled and only held on by one copper thread.

I've read posts where owners say that when they wiggle their tach filter, their engine dies, but "experts" discount this saying that its only purpose is to drive the tach and ground out the noise.

Needless to say, I soldered these wires and reassembled the harness. I took it for a very long drive and it seemed fine. Unfortunately, it didn't occur to cut these splices while the car was running.

Does anyone have experience with the tach filter failing? I know they were only on the '93, so chances are pretty slim.

DMarusa

Read CorvetteKid1983's response on this. I think this is the exact situation I had.

http://forums.corvetteforum.com/c4-t...boouncing.html

I'm crossing my fingers this is cured.

joes24

I had a similar problem for six months or more. Replaced everything in sight and still no help. When the engine started misfiring and plugs an injectors were ruled out I sent the ECM out to Cardone who remaned it for $160 and all my problems disappeared. Joe

DMarusa

Well, I didn't make it out of my neighborhood yesterday morning. After one block, it died. So, I think the tach filter was a secondary issue. This time, it didn't restart after 10 minutes. I went back two hours later and it still didn't start. I went back in the afternoon and it started right up. This episode rules out heat. It was about 50 degrees and I only made it a block.

I am going to reinstall the original coil and ICM. If the problem continues, I suppose it is the EMC as Joes24 suggests.