High idle bad TPS?

[jrgaylor]

Sometimes I get a high idle, like 1500 to 3000 rpm if it is at 1500 and I bump the throttle it will go higher and stay there. This normally happens when warm.
If I turn the engine off and then back on it will idle fine.
If I unplug the TPS when it is idling high it will return to normal.
I have tested the fuel presure regulator and have 32 lbs at idle and 42 lbs when I crack open the throttle then it returns to normal when the engine idles back down.
I pulled and read all the plugs and they look normal.
I check all the manifold/intake bolts for tightness
I checked for vacuum leaks
I cleaned the MAF and IAC.
The TPS is adjusted to about .967V and at WOT it has a reading of 4.75V
When the engine is idling high I checked the voltage at the TPS and it was .967
I just replaced the O2 sensor and reset the computer.
When performing the KOEO test I get a code for TPS out of range but when the do a KOEO test I do not get the code.
The transmission has started hunting (locking/unlock the converter) when I have the cruise on at 50 MPH on a level road
So what do you think? Is there any more tests to be done to TPS? Something else?
Joe

 

[TPLYNCH]

Is your temp gauge in the normal range or on the Hot side when it idles fast? If the computer senses an overheat situation, it will bump the idle higher to try and cool the engine.

 

[jrgaylor]

The temp was not too hot. I went ahead and replaced the TPS and on the drive home today I did not have any problems with the cruise control like I did the day before, so I will wait and see what happens in the next few days.
Joe

 

[Eric P]

My 92 did the same thing and it was the TPS also.

 

[LukeDog3D]

when you have the truck running and it is idling high, open the hood and try physically pushing the throttle closed. The problem may lie in a worn out throttle body spring.

 

[jrgaylor]

I have looked at that and the throttle is all the way closed.
thank you
Joe

 

[jrgaylor]

It has been a few days now and my idle is fine and the transmission is shifting fine also, so it appears the TPS was at fault although I did not find any faults with it with a DVM.
Joe

 

[wseemann]

Did replacing the tps solve your problem. I have the same problem on a 96 4.0 sohc. It disturbs me that you had the corect voltage on your old TPS. I hate to be a parts changer, but electronics sometimes do strange things. I have 3 trips to the dealer, and over $300.00 invested in a nofix so far. It will not do it at the dealers, but I notice more problems in hot weather, but temp runs normal.
Thanks, wseemann@srt.com

 

[jrgaylor]

Replacing the TPS solved my problems, it was only like 30 bucks for a new TPS on my 91.
JOe

 

[lonestar]

I have had the same problem that has plagued me for atleast 2 years. I replaced the TPS and was still getting the same problems. Come to find out it was because of excessive play in the TPS and the shaft due to deteriation of the thottle body shaft allowing the idle reference voltage to be to low. I ended up just shimming up the shaft with a aluminium can.

 

[wseemann]

Replaced the TPS with a new one. Still have the interminent problem. Am thinking it is a O2 sensor. Oh well, someone else's problem now. Fell in love with a next to new 03, and traded. LOVE the V8!

 

[FordExplorer18]

Hmm I need to try the aluminum can fix.