I have a 94 Z28. I have had the car for the last 20,000 miles. Ever few months I find a new problem. 4 months ago the transmission started slipping really bad. So i rebuilt the Transmission, and then bought a Trans Go shift kit.
Now its time to have another problem, or so the car thinks. Only when the car is bone cold, i mean you start the car up for the first time that day, like your getting ready to go to work in the morning. I start going down the street and give her some gas. All i get is alot of nasty stumbling then up top she seems to finally come out of it about 4 grand or so. so between 2 and 4 grand she is just jumpin really badly. It has all new plugs and wires. The only thing that I can think of is the Opti. The car has 88,000 miles on it, it is original. But I don't understand why she would only do it when she is bone cold. If you let her sit for about 2 - 3 hours, after you last drove it, she still won't do it, its only when she is first started in the morning. This isn't your normal missfire, it sounds like Vietnam going on under the hood if you lay into it, and the car doesn't go anywhere.

 

I forgot to mention the car is mostly stock, except the shift kit, rear gears, and a k&n filter.

 

I think you know what it is

And, yes it is possible. Every opti goes out with it's own bang, so to speak. Mine would run ok when cold and get worse when warm, but I have heard of others that have the same results as you. Good Luck

 

OPTISPARK

 

Check the coolant temp sensor in the water pump housing (the one that feeds the PCM). If it is not indicating a low coolant temp on startup, there will be no fuel enrichment to compensate for the cold air... sort of like losing the choke on a carb setup. It's going to run too lean and stumble until the coolant temp comes up. Then, even after letting it sit for several hours, the coolant will not have returned to the very low temp you will see on cold start on a cold morning.

A lot cheaper than the Opti.... which wouldn't be my first plcce to look, based on your description of the problem.

 

Maybe the EGR valve is sticking.

 

I have been setting a code 32 for the last year or so. Never really inhibited performance before. Now only when its cold. I am going to pull it apart tomorrow and see if its clogged.