TPS problem

[Hemiville]

Have a 92 , seems to have the typical 3-4 shift problem. Been told it probably is the throttle positioner? Can you clean these things, and how do you adjust them? Heard also that the adjustment can go out. Read bushwakrs post, appreciated muchly, but where is the screw you adjust with, and how do you take the reading with the meter, or where do you change the voltage?? What do you hook the meter up to?? Boy, this is probably one of the stupidest sounding things I've ever written. Or, perhaps , this is the way I always sound,,sic. Thanks so much for your future reply.

 

[Phil May]

As far as I know there is no way to clean them. You can try to adjust it by turnig the allen screw. My expeirence has been that It is probably wore out if it needs adjustment. There are three wires going to it one is ground, one is 5 volts supply, the other is the return. measure voltage between ground and return. I think I set mine at . 5 volts at iddle. Its been awhile since the last time I had to change mine.

 

[Wayno]

Hemiville, I have been told that you can cut the TPS switch apart and clean the contacts. The switch is glued together and you have to take a sharp knive and cut the the glue. I have never did it, but if I remeber right there were pictures on how to do this in a past TDR magazine. Either Bill Kondalay(www.dieseltrans.com) or Piers Harry(www.piersdiesel.com) told me this could be done at the Texas ralley in Kereville last year, give them a shout.

 

[BushWakr - RIP]

Hemiville,



If you look underneath the TPS you'll see a shaft that comes out the bottom. At the TOP of the shaft are two "flats" that you put an open end wrench on to adjust it. ( 7/16" or 1/2" ?)

The 3 wire connector on the TPS is were you take your test readings. The center wire is Orange I believe, and if you slide a safety pin or something thin like that into the 'socket' were the wire comes out you'll eventually touch the metal inside. Hook your "+" contact (on you voltmeter) to this and run the "-" lead of the meter to the negative side of the battery.

Turn on the key (don't start truck) and take a reading. It should be somewere between . 75 VDC and 1. 25 VDC "at rest".

Put your open end wrench on the shaft underneath and turn it SLIGHTLY to adjust. Increasing the voltage will make the 3-4 shift happen later and will also make the drop down (4-3) a little more sensitive too.

Decreasing the voltage will make the upshift happen sooner.

Somewere between . 7 VDC and 1. 25 VDC will your target. At least it was for me. I finally settled on . 7VDC, that is before the transmission job by Bill K. I don't know were it is now, or if it was altered.



As to cleaning it out, I've been told you can carefully remove the center of the top portion by dremeling/cutting the epoxy that holds the center in. Then you spray elect. cleaner in, let dry, apply dielectric grease and put together with epoxy.

Some say you can spray cleaner from the underside too. I've not had to do this personally so I can't confirm the effectiveness of these proceedures.



Hope this helps.



BTW, make small adjustments, say, . 2VDC at a time and cycle the thottle open/closed a couple times and re-check the setting. Some times it moves once the throttle has been "worked". Test drive after each. It doesn't take much to change the shift response, atleast it didn't for me.



Bob.

 

[Hemiville]

tps

thanx a bunch bushwakr, Bob, I'll try that and see what happens. I believe a "new" tps costs a bunch, so maybe I'll try to clean it?, and see what happens. not much to lose if I have to buy a new one anyway. Shifting in and out will shortcircuit your brain, kind of like a chevy owner.