I've got a base 1993 coupe that I just bought, overall in great running condition except for one small issue. Sometimes when I'm accelerating, not even very hard, it hesitates, then gets going again. I checked for codes and it gave a 32 for the EGR valve. I replaced the EGR, and the code cleared, but it's still doing it, although it seems to do it a bit less. Actually most of the time it runs fine, but every so often the engine misses or hesitates. Most of the time it idles fine, although I find if I've been running it for a while, every so often it has had an erratic idle, one time almost dying, but then it recovers. I really thought the new EGR would fix it, but there's something else that's wrong. I know there's probably a lot of things it could be, I'm not new to engines, but I'm new to LT1s, and I'd like to try to figure this out without having to take it to a dealer... the more I learn the better... Any ideas on where I should look next? There are no codes showing anymore. Thanks!

 

Let me be first to say, "OptiSpark."

There are other things that can go wrong, and they're easier to check out (by replacing the parts, usually), but it often comes down to the Optispark. do a search and you'll come up with a lot of posts on that topic.

Good luck!

 

So do all the "tune up" stuff first:
Plugs, wires, clean throttle body. clean IAC
Check for vaccum leaks (don't forget to check the bake booster is holding vaccum)
Check the connector on the passenger intake where the ECM wiring connects to the opti wiring.
Replace the ICM - don't forget thermal paste
Replace the coil
Check the MAP, TPS
Replace the fuel filter


Oh, order a replacement opti while you are at it. You need one that is first gen. Vent it or get one that is vented. Replace waterpump when you replace the opti

 

Has anyone swapped out the Opti-spark unit with the Opti-direct Ignition System from Delteq? It looks interesting, and although not as elegant a system perhaps, it looks like it would bypass all the issues the Opti-spark seems to have.

And as far as Opti-spark units go, what is recommended as a good brand for replacement? Should I just order from a dealer, or go to eBay? Any suggestions there? Thanks again.

 

Don't go to a dealer!!! Unless you want to pay twice as much.

 

Get a multimeter and a copy of the factory manual and go through the proper test sequence. Randomly throwing parts at an LT1 is not the way to go. Having said that, fire it up in the dark to make sure there is not an obvious plug wire misfire and I'd swap the plugs out as well.

 

Pull one of your plugs and check the center electrode for wear/erosion/correct gap.

Might also help to compare to a new plug.

How many miles on the car?

What is the service history/last tuneup?

Best regards,

 

Because you have a gen1 opti your sources are limited.
Do a seach here for Petris and see how their modified opti is working
There is another vendor here offering opti's
Shoot I needed a Gen2 and Summit racing had their brand opti on sale, I picked one up and it works fine. I just don't expect it to last forever.

Do a lot of research if you want to go to a Delteq. Lots of info here and around the internet. I did not go there because of cost, and complexity.

 

What did you find out?

 

Sense your new to the LT1, I have to ask; did you by chance wash your engine down? if so, your Opti got wet. Keep in mind the seller may have as well to make the engine look nice.

 

I beg to differ. This is based on my experience with missing/hesitation when I owned my 95 Corvette as well as numerous threads over the years on the forum that sometimes went on for 100s of posts that always started "must be the optispark". It could be almost anything---do a search on the word "hesitation" or "miss" and you will see what I mean.

 

Subavairpine,

I also have a 93 base coupe and experienced the samething you're currently experiencing. I did all of the above(replaced-Wire/plugs, ICM,IC,EGR Valve/Soleniod). However, It still continued to miss fire. 93rubie suggested checking the injectors. I disconnected ea injector one at a time. I discovered that the #6 was not operating at all. I've replaced all of the injectors(Trick Flo) and my 93 is running fine.

My suggestion, check your injectors...Hopes this helps

 

Sorry guys, I realized I hadn't replied to this way back when, but the problem did turn out to be the Opti... Finally got around to replacing it back in June and that fixed the problem. The old Opti was so bad inside, there was rust powder everywhere, I'm surprised it even ran as good as it did... Anyway, thanks for all the ideas, I love this car!!

 

check resistance on your injectors.
sounds just like my 91. injector resistance was all over the board.
new injectors cleared it up.