I had a p0121 light. The TPS was bad. Since i had not tuned it in 80000 miles, i changed plugs, wires, dist cap, and button. I reset check engine light and cranked it up. It started idleing rough so i increased rpm an it smoothed out. Took it for a short drive and the rpm stayed at 1850 at idle. I have checked for vacuumn leaks and have not found anything wrong. No check engine lights are on. HELP!

 

Check the throttle linkage in the engine bay. Maybe in putting things back together again something is keeping it from resetting where it should?

 

The linkage was not disconnected at first. Since i posted last i have cleaned and checked the IAC valve. Lots of carbon. Decided to clean the throttle body and check all of it. It was very dirty and i thought i had found my problem. After cleaning and installing every thing i followed the manuals instruct and reset the IAC valve. Cranked it up and the idle was about 750 rpm. Every thing looked good until the temp started up. As it warmed up, so did rpm,s. I shut off at 2900. Restarted and it went to 1850 rpm. PCM bad? Rechecked every thing and found nothing wrong. No check engine lights.

 

And the saga goes on. I finally got ck engine light again. Scanned it and my old code had returned. Po121. Took it to dealer and explained everything i had done. The tech scaned it and it showed the p0121. He reset it and restarted the engine. No code, but fast idle was there. Checked TPS and found 12 volts on the sensor wire to the ecm. Disconnected the connectors at both end and still had 12 volts with key on. Quick solution is to cut wire and replace it. I will still try to find short. I will update when i find it.