The car started up just fine today, but when I was cruising through the subdivision, the RPM's started jumping up and down, then they dropped and the car died. I had to give it gas to get it started again and launch with higher than usual RPM's to keep it from dying. Then anytime the RPM's were below 1500, the car would sputter and start to die, and if the RPM's were in the 2000 to 2500 range it would sputter really hard and the car would start to shake. It was running fine up until today.

Oh yeah, here's a brief mods list. It's a 98 Trans Am WS.6 with M6. Airbox, K&N Filter, Mac midlength headers, Off-Road Y-Pipe, Borla, Lingenfelter ported heads and matching cam , LS6 Intake, Ported throttle body, TR-6 Plugs, 10.5mm Plug wires, Suspension mods too. That's all I can think of off hand.

Anybody have any ideas what could possibly be wrong?

 

I'd check for a burned wire near your headers or a vacuum leak.

Any SES codes?

 

P0140 popped up yesterday. The guy at Autozone said it was the driver's side front O2 Sensor, but I thought that would be the rear sensor, where I have a simm due to the offroad y-pipe. Even if the simm is bad, I didn't think that would effect the engine at all. Where should I look for vacuum leaks? This seems to come and go as well. The car will run fine for a little while, then it starts acting up again.

 

Sounds to me like the O2 sensor is the culprit. They can make the car do some pretty shitty things. I would start there, and if it doesn't fix the problem, I would then start looking for a vacum leak. It could also be a bad IAC motor in the TB.

 

I'll be swapping the driver's side front O2 sensor and put a fresh simm on the back; then take it for a test drive. Hopefully that does the trick, otherwise I'll be looking for burnt wires and vacuum leaks. Any advice on checking for vacuum leaks?

 

O2 swap didn't help!!! How can I begin to diagnose what is wrong? Any and all advice would be greatly appreciated.

 

Turned out to be the crankshaft position sensor...I never would have figured that out on my own. Thanks goes out to the folks at RPM in Lewisville, TX. They do great work and have a fantastic level of customer service...that's hard to find!