I bought a 95 LT1 last month with 112k miles on it. I bought it from a woman who took it from her husband in a divorce. She claims he took very good care of it, but it came with no records. I immediately took it and had the oil changed, and the auto transmission serviced as well as the coolant. My mechanic said it actually did look like it was in good shape.
It has run incredibly well UNTIL TODAY. I was on the freeway doing about 70 when I had to hit the gas to go up a hill. When I pressed the gas, the car stumbled and shook and made a loud "ticking" sound and had almost no acceleration at all. I got of at the next exit and found some goof ball at a gas station who tried to tell me it was the catalytic converter clogged. Then his buddy came over and said the timing was off.
Heres the symptoms: If the car is idling it runs fine. If the car is sitting still and you press the gas, the engine revs fine with no stumbling. If you are actually driving the car and accelerate from a stop it will studder shake and "tick" UNTIL you press the accelerator MORE... then it will even out and run fine.
My mechanic is gone for the weekend and all of next week and this is my daily driver... any suggestions???

 

Did the check engine lite come on? You will have to pinpoint where the noise is coming from in order to get some sensible suggestions.

 

The check engine light did not come on. It is quite difficult to determine where exactly the noise is coming from since the noise is not made unless the car is actually moving. Which is one of the things I find very unusual... If the car is sitting, and you rev the engine it runs perfectly, it idles pefectly, etc.
ALSO, I have found that this only happens about 2 out of 3 times... I have a friend coming over to look at it today. My list of things to check so far are vacuum hoses, fuel filter, plugs, wires, opti.

 

Most problems are hard to catch with the car in idle, due to the fact the engine has no real load on it.

 

Ok, I thought that I would work my way up to the opti replacement... I started with replacing the TPS with no effect. Then I replaced the EGR valve (nice job putting that at the back of the engine Chevy!!!) and that fixed it. The EGR IS BLACK with carbon... And the car is running better than it has the entire time Ive owned it!!!

 

Well, so much for the happy cheary post I made two days ago... Same problem started again last night. I just picked up a waterpump, optispark, plug wires, plugs, and thermostat... Looks like Im gonna be busy today!

 

wow. well, good luck

 

Well, the problem is fixed... It was definately the optispark. The rotor was barely hanging on to the plastic part, there were several small pieces of the insider cover floating around and 2 of the contacts were severely burnt to the point of actually burning th platic around them. So it the last week I have replaced the TPS, EGR, waterpump, thermostat, optispark, all plugs and wires, fuel filter and belt...
But considering I was able to do it all myself in two afternoons with a positive result I will surely sleep good tonight!

 

Your problem is most likely your distributor. If it in any way get a drop of water on it, it will do that. Or the optical sensor inside the ditributor is bad. That has happened to me twice so far. 1994 camaro LT1.

 

This sounds like the dreaded optispark. Mine did the same thing, and got progressively worse. More times than not with stumbling issues with the LT1, it's either plugs/wires, or the optispark.