'93 olds 88 won't slow down

This car won't idle most of the time. From a cold start the engine races at around 2000 rpm. After it warms up it still races and in drive will easily pull the car along at 60mph on flat roads without touching the throttle. If I stop and shut off the car and then start it again (warm) it will idle fine until I put it in gear and drive it down the road again. Then the whole cycle will start over. Since it won't coast to a stop, the only way to get the thing to slow down at all is to abuse the brakes. The idle air controller was changed to no avail. A cracked vacuum line to the fuel pressure regulator was replaced but no change. Also, it doesn't show any trouble codes (OBD1). Could this be a coolant temp sensor failure? Help! I'm stumped!

This car won't idle most of the time. From a cold start the engine races at around 2000 rpm. After it warms up it still races and in drive will easily pull the car along at 60mph on flat roads without touching the throttle. If I stop and shut off the car and then start it again (warm) it will idle fine until I put it in gear and drive it down the road again. Then the whole cycle will start over. Since it won't coast to a stop, the only way to get the thing to slow down at all is to abuse the brakes. The idle air controller was changed to no avail. A cracked vacuum line to the fuel pressure regulator was replaced but no change. Also, it doesn't show any trouble codes (OBD1). Could this be a coolant temp sensor failure? Help! I'm stumped!


Try scanning your TPS switch with a ohm meter. I have seen your problem before and found a bad TPS switch. Did not generate a code!