The reason for replacing the throttle body was the check engine light was on and the car gave code P0121.

Before you replaced the throttle body did you have the high idle? Or only after? I would try to trace the wires off the throttle body to see if they are frayed or damaged. I would also try disconnecting the battery for 30 min or so to make sure everything is fully reset. If it didn't have the high idle before you replaced the throttle body, I would put the old one back on if you still have it to see if it goes away. If it goes away, there is a problem with the new one...if it doesn't, you know you either damaged some wiring, or the problem is most likely unrelated. Something else you can check if you have a obdII scanner, is to look at the live data and see what throttle position the car is at. At idle it should be at zero (or very close to) I believe. Lastly, you could take the intake hose off of the throttle body, and have somebody rev the engine while looking at the throttle plate in the throttle body. Make sure if moves smoothly and returns all the way back to closed as it should. I would bet your high idle is caused by the throttle being partially open, but you need to figure out what is causing that to happen.

 

Reuben,


Thank you for responding. I've read so much online about this issue and, frankly, don't know what the problem could be. Someone suggested removing the negative battery cable, pumping the brake pedal three times to drain any residual power, waiting a few minutes, reconnecting the cable, and starting the car. There was another suggestion of disconnecting both battery cables, as you mentioned, to see if that fixes the issue.



As Clint Eastwood once said, "A man's got to know his limitations." That said, I'm going to take the car to the dealer.

 

As Clint Eastwood once said, "A man's got to know his limitations." That said, I'm going to take the car to the dealer.

Always best to know your limitations...thats for sure. Let us know what the dealer finds if you can.

 

The dealer had to perform an ECM reprogram and idle relearn. That fixed it! The car runs as I'd expect.

 

Thanks for reporting back. Seems to be some mixed experiences from folks who have replaced throttle bodies as to whether or not they have required a relearn process.