96LT1355Z28

iTrader: (2)

Sunday I was running True Street in Joliet, IL. On my 3rd pass (very hot engine and trans) I missed second gear hit the 7K rev limmiter and then got it in gear. I hit third and about half way thru third I had a big backfire and the car fell on it's face, the tach went to 0. I pushed in the clutch and tried to rev it and the car was still running but the tach said 0, all the other gauges were working. I put the car into 4th and exited the track asap (15.1 @ 88 ). The car drove to the pits ok but acted as if it was loaded up. After about an hour cool down I went to load the car on the trailer and it would crank but not start. After sitting a few seconds it would fire once and then just crank like it was the fuel pump, fuel psi gauge showed 50 psi on prime and 41 psi after w/ key on. I figured I over reved the car and screwed the opti. The car was trailered home, when pushing it off the trailer (after 8 hour drive) I tried again to start it with no luck. Today I went to check spark and it fired right up, tach is working fine. What the hell could this be? If it happened once it can happen again and I can't figure it out. The only thing I have not changed is the coil (154K miles). Opti is new from dealer last December along with plugs (TR55's) and wires Accel 8mm extreme spiral core (1500 miles). I watched the video of the pass and I had a fire ball come out of the turndown as well as a small amount of black smoke, but this looks no different than when I have missed gears in the past and hit the rev limmiter. Has anyone heard of this or had this problem?!

Thanks,

Josh

96LT1355Z28

iTrader: (2)

I just went and drove the car and it runs fine untill above 48-5000 rpm. Then it will miss and backfire. Sitting still and trying to hold an rpm it's fine untill about 4500. at about 4500 the rpm's will drop almots to 3500 and suddenly surge back up as if I'm feathering the throdle randomly poping as this occurs (I'm not moving my foot!) Is this an issue with timing maybe? Iv'e got a pcm4less tune and have had no issues untill now. Also the car will randomly set a bank 2 sensor 1 O2 sensor no activity detected code. This usually only happens when the car is started and left at idle for awhile or started and then shut off several times. I figred this was just the car "loading up". I currently have no set or pending trouble codes.

flyinZ

iTrader: (15)

How old are your o2 sensors?

My bet would be Opti or coil.

96LT1355Z28

iTrader: (2)

O2's are about a year old, however I unknowingly bought Bosh sensors. I plan on replacing them with some from the dealer. I spoke with the service manager of the Chevrolet dealership I used to work at and he said the Opti has a 12 month 12,000 mile warranty on it (purchased last December/ 1500 miles ago). He said it sounded as if it was the source of the problem so I plan on taking it back this weekend. He said he will make sure it is taken care of under warranty! Hope this does it!

flyinZ

iTrader: (15)

Sweet! Id start there, since its under warranty too.

I wouldn't buy anything, other than AC Delco's...You'll be fine.

96LT1355Z28

iTrader: (2)

Ok, I take the car to put in the new opti and the friggin thing won't start to unload it off the trailer! Anyway I put in the new opti and the car starts and idles fine now, but it still doesn't want to hold a steady rpm above about 3500. Above 3500 holding my foot in one place on the gas the rpms will vary up and down almost +/- 1000 rpm's. While it's doing this the engine will pop and backfire. I have a plug and play wiring harness for my 6AL so I unplugged it to see if that was to blame, no change. I noticed while I was reving the engine from under the hood to warm it up that it backfired into the intake almost stalling the engine! This only happened once, it did also occur in the staging lanes in Chicago so I guess it's happened twice but never before. It acts as if the timming is contastantly adjusting. That's the only thing I can think of that would cause this. Is this possible, and if so how can I diagnose and or fix it?

P.S. Sorry for the long posts, I just want to put all the info out!

Thanks,

Josh

96LT1355Z28

iTrader: (2)

Anybody???

hyperzone

Is it happening at full throttle and part throttle? If it happens at full throttle, it probably isn't the O2's -- (open loop). exhaust leaks maybe? intake leaks? Then there's always the opti.... ???

96LT1355Z28

iTrader: (2)

It will vary rpm's, stumble and pop in the exhaust if it's in neutral and you try and hold the engine above 3500 rpm's. It would cut out and backfire at WOT above 5000rpm's before I replaced the opti (af few days ago) due to weather I haven't had a chance to get out and open it up to see if it still does it at WOT with the new opti.

96LT1355Z28

iTrader: (2)

Ok, I checked all sorts of stuff last night, FPR line- no leaks, opti harness- good, coil resistance- good. While chacking the coil I saw one of the pins that plugs into the harness was bent to the edge! Straightened it and tested it today. I seems to have fixed it! I noticed anothr issue though and I'm not sure if it did it before of if it even matters. When it's sitting still and I hold the rpm's above 4500 the spedometer begins to rise! It went to 20 mph at 5000 rpm (that's some steep gears!)! Is that normal or a sign of another electrical issue?