2000 Pontiac grand Prix GT RPM spikes/ and car dies

[killer99]

I just bought a used Pontiac grand prix GT 4-door from a dealer. It drives fine but I have one concern. It sometimes dies at stoplights or when I am just going slow. And it also randomly spikes in RPM and then gos down far then sets to its normal RPM. What could these two problems be? Please help. Thanks

[olopezm]

Hi killer99 welcome to the forum!

Have you checked for any codes? Is the CEL on?

Bad/disconnected sensors or faulty wiring can cause the pcm to loose a signal and revert to the default tables causing the rpm's to stay high for a brief moment when coming to a stop for example.

I would make sure the vacuum lines are ok; vacuum leaks can cause a surge on RPM's. There is a vacuum diagram under the hood.

Oscar.

[grandprixgtx00]

Could also be a flaky CPS (crank position sensor).

a bad CPS will cause the tachometer to do weird things, then the car will die.

[wolfkin_j]

hey Killer,

did you find out what the problem was? I have a 2001 gt and it has been doing the same thing to me for the past 3 months. At first the rpms would spike and droping while driving at highway speeds. Eventually it evolved to the rpms going too low and shut off when i did not have my foot on the accellerator. I cleaned out the throttle body and replaced the iac but it only fixed the problem for about a week and then it started up again. Did you have any luck with your car?