My 94 Vette (66K miles) started to have a slight miss which got worse. I took it to the local Chevy dealer and found the water pump was leaking onto the optispark. I had them install a MSD Optispark and new water pump. The car has also had a recent tuneup. When I picked it up Thursday night it was worse than when I took it in. I pulled back into the dealership and told them they had a little more work to do on it. They said it was running perfect the night before. It is still in their shop. I believe they are at a loss to what is wrong so was hoping someone might has some other ideas.
Thanks in advance for your input.

 

Hi Jerry,
Welcome to the "94 Miss Club" it took me a year to finally work mine out, but it did happen, with some patience, persistence and some advice from friends at the Forum.
My WP leaked on my opti too, and I hoped that changing it would fix my miss, but it was still there. I did a tune up, putting $6.99 plugs in and Bosche wires, but the miss was still there. What ultimately worked was a set of Bosche III fuel injectors. This fixed it although I could occasionally feel a very slight vibration at idle. I replaced the Bosche wireset with MSD performance wires and now nothing. Zero miss. At idle it is as smooth as can be. It goes through the power band like a sports car should, smoothly, and fast.
Just because you did a tune up, doesn't mean the wires are all good. Nothing against Bosche but the $150 MSD wires had no arcing or sparkle like I was getting with the Bosche. (Maybe I had a defective set. Plus MSDs give you some stickers too.) Look at the wires at night for any stray electric light shows. I put a timing light on mine to detect the pulse. If they are all setting off the timing light, and dark in the dar, then you are good there. Timing lights are cheap. They might even lend you one at Autozone. (I borrow stuff from them now and then. They have a great program for that.)
Next, look at injectors. You can easily check these (thanks to toptechx6). Take off the fuel rail covers, and disconnect an injector while the engine is running. (You have to depress the clip, and then pull it off the injector.) You should notice the engine struggle a little more. Reconnect, and do the next one and so on. The one that you disconnect where there is no change in the idle, is your culprit. After spending $50 on fuel injector cleaner additives that did nothing, I bought a new set fuel injectors from Jon at FIC, installed them in less than an hour, and my car ran like it just came off the showroom floor. They are very reasonably priced rebuilt, and sooo easy to change.
There's a sticky here for Jon at FIC, look it up if you want to see more.

 

Bob 2.0
Thanks for the reply
I'm sure the dealer put the GM wires and plugs in. They said they also did the fuel injector maintenance and I'm sure it was GM parts again. If they can't figure it out tomorrow I'll bring up the Bosche III plugs, fuel injectors and MSD wire solution to them. I live about thirty miles from Wichita, KS so my choice of mechanics is not very good. I think I'll email the local (Wichita) Corvette Club and see if they have any recommendations. I feel right now that the dealer is just throwing parts at it to try and figure it out. My mechanic days are behind me so I am kind of at the mercy of the dealership. (not good, I know)
Again, thanks for the great inputs and I'll see what they say on Monday.

Jerry