Got a '86 Firebird 2.8L MPFI, Auto. When warm and running around 650rpm at a light in drive, the rpm's will spike to 500 quick then up to 700 or so and back down to 650. This will happen about 3-5 times a minute.

She will stall once or twice driving in the city for an hour.

What could be wrong? I just replaced the rotor and plugs (gapped .045), and cap doesn't have a whole lot of carbon build up.

I am guessing that it could be a problem with the (IAC) Idle Air Control valve, which is connected to the tube from the PCV valve.

Please help

Thank you very much=)

 

i had the same problem in an Olds I use to have. Fixed everything I could think of and it turned out it was the torque converter, it was failing.
Matt

 

my car did this for 7 year's. after i started it for the first time it would run fine. if i killed it then started it back it would die at stop light's, die when i put it in reverse, and felt like it had less power. i finally put in a new O2 censor and all is well. feel's like a new car. no rough idle, or stalling, funny how no mechanic i talked to could help!