TPS adjustment

Adjusted my TPS today on my 88 4.0 AW4. Had some trouble, until I figured out, I was loosing a volt at the connector. After cleaning the connector, the adjsutment went OK. 4.64 volts going in and 82% 3.80 volts coming out. Shifts seemed to be a little latter than before, idle smoothed out a touch and the motor seems a to have a little more zip.
Question is, when testing the A wire to the gound wire at the connector, I´d get 4.64 volts, just for curiosity I tested the A wire to the battery ground, again 4.64 volts. Out of curiosity I tested the TPS ground wire to the firewall ground (and battery ground) for continuity and the resistance was really high ( 1.something on the 200 mega ohm scale). Maybe the battery is low in my multi meter or possibly there is a resistor in the ground circuit somewhere.
There doesn´t seem to be any voltage loss, through the TPS ground wire, but the resistance does seem awfully high, for a ground wire????

Add a jumper ground wire from the TPS connector back thru the loom to the firewall and a solid ground point. I just soldered another wire in with the original ground wire, no need to remove the old one. Crappy grounds in general and to the TPS in particular cause a lot of problems on the Renix XJ's.

You'll probably have to reset the TPS voltages again.

Thanx, will do :thumbup:

What should the the voltage be at the conectors?
and which pin did you conect the new ground wire to?

Thanks,
Curtiss
90xj AW4, 4.0L

They say the in voltage should be 5 volts in. the out voltage 82% of the in voltage. I had a major voltage loss across the connector it was like 4.64 volts on the computer side of the connector and 3,86 on the TPS side of the connector, cleaned it with a contact spary, which didn´t help much, then cleaned it with carbon tetrachloride (brake cleaner) figure there was some oil on the contacts, When I d got 4.64 volts on both sides of the connector I adjusted, the TPS to 82% of 4.64 volts, 3.80 volts out, throttle full closed, just out of curiosity I tested again with the motor running at idle, volts stayed the same. It runs so good now, Im affraid to add a ground wire or mess with the ground, if it ain´t broke don´t fix it.
Mine is the auto trans, A pin is input voltage, B pin is output voltage, and D pin is ground (I had to remove a snap on wire cover gizmo, to read the pin letters on the connector). The manual tranny is different. Need one of those tools that pricks the wire to make the test with, the connector connected and the ignition on and a digital multimeter, for very small acurate voltage readings. My wire colors on the TPS side were grey. blue and black/ground, different colors on the motor side of the connector.

The so called ground wire doesn't go directly to ground. I goes to the ECU by design.

I had another look at the ground wire, actually two ground wires. The TPS adjustment for the XJ with auto tranny, adjusts the TCU (tranny) side of the TPS (4 pin connector) the ground on mine is a orange with tan strip (black from the TPS to the connector). The three wire connector, is for the ECU and the ground wire is brown with a strip (black I think) and the TPS side of the 3 pin connector ground is also black. The ECU side of the TPS, is considered adjusted, when the tranny side is properly adjusted. Guess the TPS is more critical for the tranny, than for the ECU.
The orange ground wire, from the four pole (tranny) side of the TPS, goes to the TCU and goes through what tests like a capasitor, then back out of the TCU to ground. The D-3 pin into the TCU (orange with a tan strip) and the D-7 pin out to ground.
Alldata says if the standing current in the orange and tan wire to the TCU, is more than 0.1 volt, a ground can be added. Don´t really know how it would affect the capacitor, in the TCU though. Mine has 0.8 volts of standing current, in the TPS to TCU ground circuit. The TPS to ECU ground circuit, has 0 resistance and no standing voltage (looks good).
If I´m wrong, please somebody explain it to me, I spent hours with an old wiring harness in my driveway this morning following wires. Took me awhile to kind of figure it out. I never did find the TCU ground (D-7 pin to chassis).
My problem is an occasional. lock, unlock, lock, unlock, chatter at almost exactly 2000 RPM or about 1/3, pedal, I can accelerate right through it with no problem, but in fourth and a steady 2000 RPM, it will chatter on occasion. Don´t really know if it´s the low TPS in voltage or the TPS to ground resistance or just a bad TPS. But it did improve some, when I cleaned the connector and the TPS in voltage went up some and after the TPS adjustment.

8Mud said:

I had another look at the ground wire, actually two ground wires. The TPS adjustment for the XJ with auto tranny, adjusts the TCU (tranny) side of the TPS (4 pin connector) the ground on mine is a orange with tan strip (black from the TPS to the connector). The three wire connector, is for the ECU and the ground wire is brown with a strip (black I think) and the TPS side of the 3 pin connector ground is also black. The ECU side of the TPS, is considered adjusted, when the tranny side is properly adjusted. Guess the TPS is more critical for the tranny, than for the ECU.
The orange ground wire, from the four pole (tranny) side of the TPS, goes to the TCU and goes through what tests like a capasitor, then back out of the TCU to ground. The D-3 pin into the TCU (orange with a tan strip) and the D-7 pin out to ground.
Alldata says if the standing current in the orange and tan wire to the TCU, is more than 0.1 volt, a ground can be added. Don´t really know how it would affect the capacitor, in the TCU though. Mine has 0.8 volts of standing current, in the TPS to TCU ground circuit. The TPS to ECU ground circuit, has 0 resistance and no standing voltage (looks good).
If I´m wrong, please somebody explain it to me, I spent hours with an old wiring harness in my driveway this morning following wires. Took me awhile to kind of figure it out. I never did find the TCU ground (D-7 pin to chassis).
My problem is an occasional. lock, unlock, lock, unlock, chatter at almost exactly 2000 RPM or about 1/3, pedal, I can accelerate right through it with no problem, but in fourth and a steady 2000 RPM, it will chatter on occasion. Don´t really know if it´s the low TPS in voltage or the TPS to ground resistance or just a bad TPS. But it did improve some, when I cleaned the connector and the TPS in voltage went up some and after the TPS adjustment.

Click to expand...

OK i know this is a REALLY REALLY old thread, but i happen to come across it and it raises some questions.

First off i want to say that i have added a ground wire to the TCU side of the TPS to eliminate any ground issues. I did this awhile ago. My TPS is adjusted correctly etc.

Now I'm wondering if adding that ground wire is not a good idea.

The biggest reason why i say so is because of what you said 8Mud:

8Mud said:

My problem is an occasional. lock, unlock, lock, unlock, chatter at almost exactly 2000 RPM or about 1/3, pedal, I can accelerate right through it with no problem, but in fourth and a steady 2000 RPM, it will chatter on occasion. Don´t really know if it´s the low TPS in voltage or the TPS to ground resistance or just a bad TPS. But it did improve some, when I cleaned the connector and the TPS in voltage went up some and after the TPS adjustment.

Click to expand...

I guess i have a slightly similar problem that may or may not be attributed to this.

(90 RENIX)

What happens in my cause is what i can best describe as an idle "float".

No matter if the engine is hot or cold it does this:

RUNS GREAT BTW! this problem is more annoying then anything.. I can press the gas when it is happening and accelerate just fine. No vacuum leaks nothing else wrong with the Jeep etc...

Lets say im going down the road at 55mph keeping speed with my foot on the pedal. If i let off the pedal, depending on how fast I'm going, the RPM's will drop to a specified RPM, and then slowly start making its way down to idle RPM range since i am no longer giving the Jeep any gas via the pedal. (aka de-accelerating)

Make since so far?

OK .. imagine this... with my foot off of the pedal, the RPM's making their way down to idle RPM range, RPM's reach approx 1000 RPM's. The RPM's now start "floating". They start moving back and forth between 1000, and the next line up on the tach which i think is approx 1350 RPM's. You can hear the engine go with the movement of the tach when this is occurring. Its almost acting like I'm slowly giving it just a tiny bit of gas and letting off .. over and over again. The Jeep has to be going fast enough in a certain gear (to work its way into that 1000 RPM range) with my foot off of the pedal de-accelerating for this to happen. I haven't heard of anything like this.. so i have been trying to figure it out. Ive tried multiple TPS's to see if one would cure the problem, but with all of them adjusted (i think I've tried about 5 or 6) the Jeep runs the same and acts the same.

The only other thing i have attributed this too is something with back pressure. I could be way off base, but it was part of my thought process. The reason why is because i have basically a stock exhaust with a gutted cat... i dunno!

Does anyone have any input to this. I understand im nit-picking since i have nothing else wrong with the Jeep (for now... that could change tomorrow lol!). Im just really anal, and i would like to see if i could get it to stop doing what its doing.

Thanks very much for your time.

Anyone?

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