well searched TPS issues and still have questions? any ideas?

1989 renix xj aw4


so ive adjusted my TPS every so many months for years.
but now im stumped.

i started getting some erratic shifting and early shifting and even the torque converter staying locked and then never locking in the past fews.

first thing went to the TPS, input voltage was off. like aorund 1.06. , not 4.7 ish (my output voltage is adjusted accordingly )

so i threw a spare used TPS on.
that also reads low input voltage.

my guess is that both TPS's are bad, since they are both used, and that my spare was junk to begin with (Junkyard spare)

so my next question is this:
is it reasonable to believe the problem is 2 bad TPS and not something else?
i measured voltage across the TPS harness after unplugging the TPS and i get around 4.73 volts.

output voltage on both 3 and 4 prong (tcu and ecu sides) are both around 1 plugged in and goes up to 4.7ish with the TPS unplugged.

this makes me think that voltage is getting there and the TPS is bad.

resistence across the tps B to A terminals is like 150 ohms.

the output voltage is around 3.83, and the input is around 0.7 - 1.13.

also, while doing this i spliced the ground wire to the battery ground as well.

i run 0 gauge welding wire for grounds all over the battery to block to firewall.

i guess im stumped and i dont know if i should just get a new TPS or be looking for other electrical problems.

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

so this article that i usually reference but havent read in a while actually makes it seem like its maybe ok.

damn. if its not the TPS what else?

TCU?
solenoids?

is there a easy way to test the tcu and the solenoids if the TPS is ok?

PM me with your email address and I'll send you some easy to use TPS instructions. Many of them out there are wrong, including some on lunghd's website.They include a quick check for your sensor grounds, which if bad, can cause all sorts of problems. It's an easy fix if that's the case.

Since you have an 87 , it has the dreaded c101 connector on the firewall above the brake booster. Unbolt the 2 halves, clean out the tar-like crap with a pocket screwdriver, spray with contact cleaner, wipe out with a cloth. Add dielectric grease and bolt back together. Every important signal needed for your fuel injection system to work properly, except a few, run through the c10.1

cool. ill pm ya now.
ill pull apart the c101 as well.

Do the c101 first.

haha. i have an 89. i just realized i dont have a c101.
im special .

although i re back probed and was getting funny reads coming from the ecu side of the connectors, from the sensor side i was getting the proper reads:
4 prong(tcu)
input voltage was 4.72 after better ground
adjusted to 83% at 3.92

3 prong(ecu side)
input was 4.89
output was 0.65 (should be closer to .8 i think?)

anyway, the tcu side seems ok.
i am wondering if the output on the ecu side is too low and causing issues?

Nevermind the ECU or TCU side of the connectors. Pay attention to the sensor side only. Have you checked your sensor ground circuit as described in the beginning of the instructions? Takes about 20 seconds to do. If that circuit is compromised these sensors will give false info to the ECU:
TPS, IAT, MAP, CTS. Those are important signals.................

yah the ground is good on the 4 prong side, im gonig to jump the 3 prong side to the battery and test the tcu ground next as well.

cruiser54 said:

Since you have an 87 , it has the dreaded c101 connector on the firewall above the brake booster. Unbolt the 2 halves, clean out the tar-like crap with a pocket screwdriver, spray with contact cleaner, wipe out with a cloth. Add dielectric grease and bolt back together. Every important signal needed for your fuel injection system to work properly, except a few, run through the c10.1

Click to expand...

That.

WNC95xj said:

That.

Click to expand...

No foolin'. Nobody wants to believe that for some reason.......

Blonde: Probe the brown with white tracer wire from the TPS flat 3-wire connector with the one of your leads and place the other probe on your negative battery post with the meter set on ohms. What does the meter read?

the resistence for the ecu side is 0.14 ohms, the resistence for the TCU side is .04 ohms.
i came to a compromise with adjusting the TPS.
if i adjusted the TCU side to 83$ i get only 15% at the ECU side, if i adjust the ECU to 17% i get less than 80% at the TCU side, so i adjusted the ECU side to 0.8 /4.9 (reference) and am about 16.4% at the ECU side, and am at 80% at the TCU side with 3.77/4.71(reference) which i think is a reasonable compromise.

is the compromise a good thing or should i just do it right to the ECU side only or the TCU side only and go from there?

i ran an additional ground from the TCU side ground to the battery to get the better voltage, i plan to do the same at the ecu side tomorrow night. i will also check the actual TCU itself for resistence in the ground to the TCU.

i also get 0.14 ohms at the MAP sensor for ground resistence, i couldnt get a good read on the CPS ground, so ill try again tomorrow.

ill also check the ground at the ECU as well.


i also checked the resistence from the negative battery post to the fire wall and it is .02. i run 2 gauge from the back of the engine to the firewall and 0 guage from the battery to the block and clean it periodically and hit it with dielectric grease occasionally as well.
i have an 89 so i dont have a c101.

Wanna do this the easy and complete way? Can you solder? .14 ohms of resistance in any of the sensors: IAT, MAP, TPS, CTS indicates some poor crimps in the harness that are easy to find and fix. Easier than what you're doing.

cruiser54 said:

Wanna do this the easy and complete way? Can you solder? .14 ohms of resistance in any of the sensors: IAT, MAP, TPS, CTS indicates some poor crimps in the harness that are easy to find and fix. Easier than what you're doing.

Click to expand...

????? .14 ohms may just be the meters internal impedance. .14 ohms is very low and not a problem. My digital meters usually show .6 ohms on a dead short probe to probe. If the total ground resistance with a meter that can not be zeroed is less than 1.0 ohms, it is good to go IMHO.

cruiser54 said:

PM me with your email address and I'll send you some easy to use TPS instructions. Many of them out there are wrong, including some on lunghd's website.They include a quick check for your sensor grounds, which if bad, can cause all sorts of problems. It's an easy fix if that's the case.

Click to expand...

Why not just post these "easy to use" TPS instructions for everyone to see?

i can solder yes.
i did get a nice drop from .12 to .04 at the TCU side after splicing in a new ground. i figure i might be able to slightly increase grounds all aroud by doing so?
i plan to solder in all of the spliced grounds.

MT Mike said:

Why not just post these "easy to use" TPS instructions for everyone to see?

Click to expand...

I asked you to let me make them a sticky months ago when you busted me for posting a link to copywrighted material and you never responded. I'd love to do as you ask.

Ecomike said:

????? .14 ohms may just be the meters internal impedance. .14 ohms is very low and not a problem. My digital meters usually show .6 ohms on a dead short probe to probe. If the total ground resistance with a meter that can not be zeroed is less than 1.0 ohms, it is good to go IMHO.

Click to expand...

I agree that .14 Ohms is not too much. But the OP probably didn't wiggle the harnesses to see if he could get more resistance. And, he wants to add a bunch of grounds, I'll give him the easy once and for all cure.

cruiser54 said:

I asked you to let me make them a sticky months ago when you busted me for posting a link to copywrighted material and you never responded. I'd love to do as you ask.

Click to expand...

In order for your magical TPS instructions to be made into a sticky, they need to be posted first. :twak:

Check your PMs please.

cruiser54 said:

Check your PMs please.

Click to expand...

Mine?

ill take whatever help i can get.
yah i was gonna add a new ground to both sides of the TPS and tie it into the firewall ground.