I have no idea, whats wrong with the LT1
 

46,000 miles on her, so shes got some milage but not too bad. Friday night after I got out of work I drove down to my dads house, about 15 miles away, hung out with him for maybe a half hour, got back into my car, backed out of his drive way, had a backfire. Got out to the mainstrip where the speed limit is 40mph, my foot is all the way to floor with her constantly backfiring doing 20mph. About half way home (4 miles) I had a retarded idea to take off the oil cap, I was at this point able to get upto 40mph with constant backfiring but I was now in a 55mph. I got home parked her b***h @$$ in the driveway where I left her till Sunday.

Sunday morning, I got up early, checked out out my car, realized my air intake was loose, tightened it, fired her up, she was fine. Had a wedding to goto that afternoon so thats why I got up early to fix it. Anyway, on my way to the wedding I was in a 40mph zone with cruise control on, and I feel my car rocking, look at my rpm guage, and my idle is fluxuating between 300rpms (Not at 300, but between something like 1100-1400). Had a backfire, disengaged cruise control realized my rpms were staying and I was losing mph. I parked her on the side of the road this time, had a friend pick me up and bring me to the wedding. About 3 hours later, I went back to my car, started her up and got her home.

No idea what this is, but when she starts doing her thing, my engine shakes so much my exhaust is bouncing on my subframe. I ruled out the air intake, I even liquid checked all the seals, air intake is not the problem. I also think that she started up sunday because she was cold, like she was after the wedding, and when she was hot (when I left my dads and when I was driving) she started doing this.

I'm not gonna reject any ideas on what this is, so if you got an idea, I'm opened to opinions. And if you got a easy way, or anyway to check to see if thats the problem, please post that too.

-Jay Frat

Sounds like a misfire, I would change the plugs and wires.

Oh, sorry, forgot to mention that I just had the plugs and wires changed about 1,000 miles ago.

yeah either a misfire or youve got serious valve train problems.

Could it be the Opti? I figure its not the spark plugs/wires because it only does it when its at operating temp. so I figured if the plugs our fouled it would do it anyway no matter what temp.

Valve train=GREEEAAAAAAAAAAAAAAAT

My girlfriends Buick was doing the exact same thing 2 weeks ago. Her car would shake like hell when it was warm and couldn't go past 50 kmph 2 of the cylinders weren't firing.. They first thought it was the coil pack but it was the ignition module.

Its the Opti-Spark and the EGR Valve, they both went. :confused:

Took it to a shop where a friend of mine works, he hooked it up to the computer, showed the codes for the EGR and the Opti he checked both and neither one worked.

EGR got today, got that fixed, tomorrow is the Opti.