tps #3

what are some (realistic) potential causes for tps malfunction/failure?

-I've heard pressure washing (near there) isn't smart

-Faulty (new) aftermarket parts seem to be a recurring theme in sensor replacement threads

-- How about a bad voltage regulator? what does the tps voltage get regulated by? my alternator tried to fry my wiring a couple months ago with near 17volts!

- has anyone else tested the susceptibility of a tps sensor to crushing from a 24oz waffle head framing hammer?
I'm probably not the first one nor will I be the last one to try it...

But I am pretty serious about finding out why I fry these expensive and important sensors, so your help is appreciated!
phil

Renix? On mine I couldn´t seem to get the same reading twice, turned out to be some oil in a connector. If you have a Renix, the gorunds are very important, the TCU and ECU grounds are on the dipstick holder.
There was a TSB, about moving the grounds to the opposite side of the battery ground cable, because of grounding issues. I soldered all of my grounds into one lump.
Noticed earlier, you mentioned something about your tranny, that reminded me of a bucking issue. Is this your problem? Easy to confuse an engine buck, with a tranny problem, torque converter issues and an engine buck, act almost identically. What made you think your TPS´s were bad?
If you have the AW4, the TCU half of the TPS, gets it´s voltage from the TCU and the ECU half from the ECU. I notice don mine, the imput voltages are close, but not identical.
The only bad TPS, I´ve had was one that had a hitch at a bout 1/3 rd throttle, I could see it when I tested it from stop to stop with an old analog ohm meter. Funny but after i´d found it and replaced the TPS, I found a TSB or recall for TPS on my 88, for exactly the trouble I´d found.
If you don´t have a Renix, some of this is applicable, some not.

the first tps replacement was whacky readings at idle and bad driving, the second was because the tcu went out while driving a pretty major mountain pass and left me governor shifting, and finally I am back to the whacky tps readings/bad idle/bad driving and am considering the hammer
I'mma go check the grounds now though.... I've sprayed all my connectors inside and out with the cleaner and dielectric'd the crap into them

What year XJ? I´ve never tried to test a TPS, with the motor running. Usually set them, motor stopped with the key in the run posiition. With the exception of checking my imput voltage with the motor running, I was curious if it changed much, mine changed about .2 volts higher. Another quick test, is to test the ground wire for the TPS, from the wire to battery ground, For standing voltage, there will be a little standing voltage, because the TPS grounds through the TCU, then to the motor ground. There is a little built in resistance in the TCU, but not much. If your standing voltag is any more than say .3 or so, you probably have a bad connector and/or ground.
Set your meter to the highest resistance scale and check for resisitance should be zero (or near enough), then smear a little of the di electric grease on a probe and see if there is any resistance. All di electric grease isn´t equal, it may cause a resistance problem with the fractions of a volt found in the TPS. I use a little conductive paste on mine, actually improves the continuity, just got to be carefull the stuff conducts electricity almost like wire, use very little and don´t smear. I use a toothpick and am very carefull where I put it.
Where the cable makes the turn at the rear of the fuel rail, is a classic spot to have broken or frayed wires.