TPS Coming Out of Adjustment

[dusthomps]

Guys...



The TPS on my 92 somehow has been coming out of adjustment. About every two weeks or so the truck will start dropping out of OD at 55 and then I readjust the TPS and everything is fine. How does the TPS keep coming out of adjustment and is there anything I can do to prevent it from continuously coming out of adjustment???



Dustin

 

[BushWakr - RIP]

Dustin,



It could a couple things, one is the TPS malfunction as you note.

When this happens, and you reset the TPS do you find that the last setting is actually changed??? If it was set at say... oh, . 75vdc did you find it was no longer there but higher/lower??

When I set mine, I make sure to cycle the throttle open/closed several times, then recheck the value I just set to confirm it has been retained.



If you find that the value is still intact or darn close +- . 05vdc then the TPS is most likely not the culprit.

If it is the TPS, you'lll need to remove the black TPS body itself from the bracket its sitting on. There are commonly two screws on diagonal corners holding it down. Carefully remove those screws and lift the TPS body off. You'll see the underside has a slot in it, and the remaining part on the bracket has a key (both plastic). Turn the TPS over and spray some electrical contact cleaner into the bottom of the TPS. Use some compressed air and blow out/dry out the cleaner. Re-install, set your voltage and test drive.

Some have actaully used a dremel tool, and carefully removed the center section from the top of the TPS, cleaned the innards well, applied some dielectric grease, then epoxy'd the center back on. A number of guys have had good result doing that.

I think there are some pics in my readers rigs gallery that show the center removed if you want to look.



Your symptoms also possibly sound like the speed sensor. It commonly effects the OD shifting. One of the main symptoms of this is the speedo dropping to 0 or the speedo thrashing up and down at random times/speeds.



Get back to us with some more info on symptoms/observations.



Bob.

 

[dusthomps]

Bob...



The last time I adjusted the TPS, the volt read out was too high and yesterday when I redid it, it was too low. I'm talking a swing in 2+ volts in both directions. This was the third time I have readjusted. I have removed the TPS and sprayed it with contact cleaner and dried as you noted. The speed sensor was replaced six months ago and speedo has no fluxuations. After adjusting, I run the throttle open and close about a dozen times to make sure the volts are still in spec. Then I take it out to see how the OD is doing and get after it quite a bit to see if I can get it out of adjustment. OD works fine and when I get back home, volts are still where I set them. So far I cannot recreate the problem, but in about two weeks or so it will start again. The last three adjustments have lastest roughly two weeks at a time. #ad

 

[nascar mark]

I got a hunch.

For the heck of it pull your tps and check to see if the little bolt that slides into the top of the throttle is tightly screwed into the plastic head of the piece between the tps and throttle top. It must be really tight or you will have to remove it and try locktite or glue so it holds better.

 

[boatpuller]

I think that's the same problem I'm having with mine, after about 50-100 miles it goes out of adjustment and then won't go into overdrive until 60. I'll try the lock tite next time.



Caleb

 

[dusthomps]

Mark...



I'll dig into on Saturday when the truck is around... my old man has been running it to work and back and he's on 2nd shift, (I work 1st). I'll post my findings as soon as I look at it. Thanks again for the tip... .

 

[dusthomps]

Mark...



Pulled the TPS today and checked out the little bolt that screws into the plastic head for the TPS. It seemed tight, but after putting some wrenches on it I didn't feel it was tight enough. Put some locktite on it and put it all back together and adjusted the volts accordingly. Hopefully this will solve my problem for good!