91 formula 305 tpi. Runs great, except for some kind of electrical issue. Randomly at idle, when cold or hot it will idle high. Plugged in a snap on tool for live data at a shop and saw that my throttle was at 9% during the high idle and tps voltage was also high. The tb was completely shut. The tps was new and had a new connector too. After a few minutes it would go away and idle perfectly at 0%throttle but the tps voltage seemed to move a bit still. Sometimes it only lasts for seconds sometimes 10 min. Happens when driving too, but at idle the tb is not moving one bit. Checked ground on passenger side cylinder head both sides checked for corrosion and tightened down. What other grounds could affect it? Maybe a bad relay? Anybody got a wiring diagram for the tps? Any help would be appreciated.

 

 

Are you sure the throttle blades are completely closed? I don't think a high TPS voltage itself will generate a high idle condition.

 

yes I am 100% sure I even gave the throttle a twist to make sure it was shut. And if the tps is reading high it will open the iac. Just need to figure out why the tps is reading high.

 

Verify the 5VDC reference from the ECM is not varying. Also be sure the ECM grounds are solidly connected. ECM connectors and the ground at the rear of the right head are good starting points.

 

thanks, I'll get back to you to tell you my results. Crossing my fingers that this is the issue.

 

just verified the 5vdc and it changes from 5.04 all the way to zero after it idles wacky. It keeps idling weird and the 5v reference goes all over the place and eventually reads zero. Sometimes it comes back then does it over again. When it's idling normal, the 5v DC reference is 5v and fine. Also my engine seems to have the ground on the passenger side and it was good. We loosened it up then tightened it down and it was fine. Do I need a new ecm? Or should I do some more testing on the ecm? How would I go about that and do u have a diagram? Thanks a million for the help, I never would have got this close to the issue otherwise!