I own a 1995 LT-1 Corvette with less than 30,000 miles. Recently while driving it it developed a significant engine miss at idle. As a few days went by it became more noticeable. I decided to take it on an extended drive for a day. After about an hour it started missing and finally quit and wouldn't start.

After getting it back to my garage I checked for DTC codes and found none. The fuel pressure is 41 psi with the key on and engine off so I don't think it is the fuel pump.

After sitting overnight I can start the car and it runs like a top. A few minutes later it starts to miss again and finally dies if I don't keep the rpm's above 3,000.

I'm thinking it is an electrical problem, possibly the PCM, but I don't have the proper diagnostic equipment to test it.

I am tempted to replace my PCM with the hopes it is the problem, except I don't like to go down the path of replacing parts for no reason.

Has anyone had similar problems? If the described symptoms are common to a faulty PCM I would replace it in a heartbeat. It is going to cost much more for me to have some shop work on my car than the price of a new PCM. I am unfamiliar in my area and concerned about finding an honest and knowledgeable repair shop.

 

It's never a good idea to throw parts at a problem. What part of the world do you live in? Maybe a forum member can point you toward a shop that can diagnose for you.

 

After reading another thread about failing optispark systems after a water pump replacement I'm thinking it may be the optispark as I just replaced my water pump a couple of weeks ago.

 

I would vote for the Opti.

 

my '91 does something similar. stalls after a period of driving. will start right back up though but when rpm drops to idle it quits again. had it in the dealer shop but couldn't replicate the problem and did some repair to no avail. how did you resolve your issue?

 

does your car run rich?

 

I have been fighting a similar issue with my 94 for 3 months now. It runs great until it stalls. Let it sit for a minute and it fires right up then stalls going down the road. I am getting DTC 36 & 42. I ran diagnostics on it and it appeared that the PCM was bad. I took it to NAPA and they sent it out for a rebuild. Rebuild company said nothing was wrong with it. I had the ICM tested and it passed also. I'm going to run a few more tests, but it is looking like an Opti-Spark issue.

 

My 92 seems to run rich and cuts out when it gets warm. Does running rich tell you something?

 

In my original post I failed to mention that I had just replaced the water pump. In another thread I found that many opti-spark distributors fail shortly after having the water pump replaced. I have ordered a new opti-spark distributor and will put it on. I feel certain, based on the information in the other thread, that the opti-spark distributor will solve my problems. If not, I am only out less than $100 and have a new distributor!!

 

I hope you didn't order one off flEaBAY.

 

After replacing the opti-spark distributor the engine started and ran perfectly, for about 30 minutes, and then started doing the same thing, missing badly and finally stalling. I'm wondering if having disconnected the battery that the PCM would reset itself? Is a PCM susceptible to heat? Will it work fine while cold but then fail when warmed up? No DTC codes are being set. The fuel pressure is 41 psi, which is normal, so wouldn't that mean the fuel pressure regulator is OK and therefore not running rich?

 

You really need to go thru a methodical diagnois to track this down. You can't guess and throw parts at it, its too expensive, frustrating and you have to be lucky to fix it that way. Follow this thread:
http://www.camaroz28.com/forums/showthread.php?t=601565

I followed it to track down a horrible miss and it turned out to be the coil.

 

A bad Ignition Control Module (ICM) can cause the problem your car is exhibiting, too.

 

After ordering a new opti-spark distributor off the internet ($84.50) and installing it, my car ran but did not run well. I finally took it to a shop for diagnosis and found the new distributor was defective. I've since ordered and installed a new distributor from Jeg's Automotive ($270) and so far everything is OK, the car runs like a top.

 

I would not necessarily conclude it was the opti but perhaps it was. Just do a search for "missing" or "stalling" and you will be amazed. I seem to recall at least one member who ended up changing everything that you would logically think of (opti, plugs, wires, ignition module, coil, etc.) and never successfully tracking this down.

My car went through a couple of periods where there was missing--sometimes quite noticeable. In all of these instances the car NEVER threw a code. One of the times I changed the opti (at the dealer) and the missing returned after a while. Replaced the opti again with plugs and wires and that seemed to work (until one of the wires accidentally touched the exhaust manifold causing intermittent missing). Replace those wires with MSD and car was fine after that.

Doug

 

Do the regular tune up procedures, plugs, wires, and ignition module as mentioned above. The ignition module can sometimes fail when it gets hot. These are items that need to be replaced anyway, so you aren't throwing money away. There's a good chance this could solve your problem. The ecm would be farther down the list.