99 Park Ave engine is racing

I have a 99 Park Ave with about 200K miles on it. I have an intermittent problem where the engine races as if the accelerator is being pushed to the floor. If you stop the car and put it in park, the rpms are above 3000. When you shut the car off and restart it, it works fine again, usually for several days or longer. This problem has not caused any codes to be logged, yet. Has anyone had this problem?

Without a code, I'd guess the TPS Throttle Position Sensor

Actually, an out of range TPS would be one of the first things to set a code. The Idle Air Control (IAC) can be more difficult to troubleshoot during the initial phase of failure. In many instances, high idle or stalling ends up being an idle control motor at its upper, or lower limits, or a failed motor. A good scan tool could help identify this problem without waiting for a DTC to set. In addition, a vacuum leak can cause this, so don’t replace the idle control motor until you’ve evaluated the possibility of a vacuum leak. :headshake

On a 96 Ultra, it turned out to be a bypass for the supercharger. I don't know where it is or what it looks like, but it cost a small fortune to have fixed.

On a 96 Ultra, it turned out to be a bypass for the supercharger. I don't know where it is or what it looks like, but it cost a small fortune to have fixed.

OEM replacement bypass valve for Eaton blowers is available for $39.99 @ ZZ Performance (http://www.zzperformance.com/grand_prix/aboutus.php)

http://www.zzperformance.com/products_img/840_3.jpgOEM replacement bypass valve for Eaton blowers.