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FRIGGIN' TPS

cbtb87

NAXJA Forum User
Location
oregon
'88 xj,aw4,4.0 litre. To start: checking tps voltage in, was at 4.60v . Bad ground. Ran jumper ground now is 5.46v. Is that ok??? Next: check output voltage, is .82 . Sounds great right? Wrong, moved tps to see if output would change. Doesnt change, still on .82 . What the heck is going on??? I am about ready to burn this P.O.S. to the ground. :mad:
 
First, are you sure you're back probing the right terminals? What reference are you using? Are you manual or auto?

4.60-ish sounds like mine. Book says approx 5 v.
 
Ok , your TPS is two parts.
One for Transmission computer, and one for engine computer.
Without actuall going outside to look, there are 6 wires.
Two feed 5 (+/_) volts at opposite ends of the TPS.
The other opposites are ground (or very near)
The middle connectors should read "either" approx .8 or 4.2 volts at closed throttle with the key on run. They both should smoothly vary with throttle position each in the opposite meter direction to maximum. Either ground (very low volts), or B+ (very near 5 volts)
Keep in mind with my '88 Renix, I noticed after several minutes of a no-run situation, the 5 volts supply gets shut down. Anyone else confirm this please? This would suddenly become a very confusing test procedure at that point.
Not sure where the wisest place to connect voltmeter negative lead given all the Renix ground issues. I would go to the battery I suppose.

Side thought, I think I remember someone very knowledgable in this forum say they had their TPS plug connected backwards for one reason or another....
this isn't a "ran good until I started cheking out the TPS" situation is it?

You CANNOT use a strictly digital voltmeter to see how smooth TPS response is, but it is fine for upper and lower limits...

I love my Simpson 260
 
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A and D are input---B and D are output, right? I just dont understand why the output doesnt move when the tps moves. I have looked at alot of threads about tps adj. Never seen my problem. BTW its auto.
 
What led you to start checking the TPS?
Did you remove the plug and re-insert it correctly?
Your original post did say AW4, so I assumed it was auto.
I'm not sure what pin designators are assigned.
 
high idle. now it wont shift from 1st. What was that phrase......oh yeah. If it aint broke dont fix it. Words to live by!!!!
 
Search for the "RenX files" thread and if you will go through all ten pages you will be a Renix TPS high idle and transmission TPS issue expert. It has a few links IIRC to some sites with photos to.

If you are testing the TPS properly, probes in the right places, have a working ground on the TPS side where you are testing it and if the TPS is installed correctly, then your test results indicate a TPS internal short of sorts, or a constant output voltage from the TPS, which means it IS TOAST, defective, real junk, time to replace it.

Also a fixed volatge on the output side of the TPS that is not changing as you move the throttle (or move the TPS at the throttle body) and if measurement is on the transmission side of the TPS (Square connector) then that would be the cause for transmission to stay in first gear. So that sounds like confirmation that your TPS is shot.

TPS is !!!1.

I made some conditional statements above, because if the the ground connection is bad on the TPS to wiring harness connection that could cause the same problem.

5.0 volts on the ECU is normal. More than that is maybe OK, but not normal. Less tha 5.0 volts input means a dirty contact somewhere which can lead to random variable idle speeds if the contact gets better or worse with wiring contact motion.

I would check and make sure the meter is working right, check that the battery is not dying, is the meter digital or analog? Good analog meters must be zeroed manually before use!!!
 
From 05-03-07 Re: bad idle and poor running

Ecomike said:
This is going to sound stupid, but make sure the TPS and O2 sensor connectors are attached backwards. I have an old wiring harness and I discovered the hard way (drove me nuts for weeks) that they could be attached backwards on the older renix harness once some of the plastic clip stuff breaks off. I made a post on this last year. It still ran with both attached backwards, but the gas mileage tanked and it ran rough.

I knew i wasn't crazy.
 
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