I have a 91 Buick park Ave that is experiencing these symptoms.

When starting from a cold start the engine will turn over, reach around 1000 rpm, then die.

When applying gas and turning the key the engine revs up and idles at a higher rpm (say 3000) once gas is released the engine dies.

If the gas is held the engine will cycle through a couple different rpms. For 5 to 6 seconds it will idle at the higher rpm (say 3000) then drop 1000 rpm for 2-3 seconds (down to 2000 rpm) then back up to the higher rpm (3000) for 5-6 more seconds.

The problem is in the Idle Air Control Valve not working consistently. I've replaced the IAC. It is supposed to behave by traveling out when given power and in when the power is cut. The out behavior works fine while the in behavior is sporadic.

I've tried replacing the ECU, IAC, TPS, and the O2 sensor. There are no continuity issues or vacuum leaks.

Any ideas would be helpful.

  • Have you done a reset for the IAC since you replaced it? Have you cleaned the intake passages for the IAC? For the throttle body? Jul 31, 2015 at 19:21

2 Answers 2


If it has a MAF sensor, check the connection from the MAF to the intake manifold. If there is a leak, it will be sucking air past the MAG (unmeasured air) and the car will be running very lean. A quick test - disconnect the MAF and the engine will revert to speed-density mode and drive more or less normal. Many GM cars switched to MAF in the late 80s. Not sure if your car did.


I'd check the engine coolant temp sensor reading to make sure it's reporting the right temps. I'd also check for vacuum leaks.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .