Just bought a 93 Z28 this week that has a 97 LT1 motor in it with 60,000 miles on it.
Before I bought it, the car sat for about 8 months without being driven, just started up occasionally.

At anything over 4000 rpm it's missing and popping (when I hammer it), and running really rich.
I ran through all the old gas that was in it and put in a fresh tank and it seemed to get a little better (I thought the bad gas was the problem). I noticed the O2 sensor on the passenger side was broken (the wire was not connected/broken). I changed that sensor today and connected it, thinking that could also be contributing to the problem. Now, it's worse than it was before. Any time I put it to the floor it pops/misses really badly at about 4000 rpm, to where it won't shift until I let off. It's fine at lower rpms. It's not throwing any computer codes at all.

Any ideas/suggestions?

 

tons of posts about this... do a search...

for me it was a wasted coil wire.

 

It could be the Opti rotor getting loos, fouled plugs, bad plug wires or several other things.

WD

 

I had this problem too. its almost like the engine hits its rev limit. my problem turned out to be the the coil wire that was frayed and broken. unfortunately i had to buy a whole new set of spark plugs to get the wire i needed. so check that, but it definately sounds electrical