New to Jeeps and need help

Hey Eveybody. I just got a very nice 1990 2rd Xj. Its only got 145k on it and is in amazing shape without a single spec of rust.

But it has a few issues. One of them is I just cant adjust the TPS. I have spend days reading about the process of adjusting the TPS.

It all started with a strange stutter and miss fire at 2000 rpm when very light on the throttle.

I got a new TPS thinking that this could be a good way to start. So i hooked it all up and got a voltmeter to test it out. I started with mesuring the voltage at terminal A and B on the squire plug. It sais that i should get 5V i got about 4.5V which I was told is ok. After that i mesured the voltage between B and C and got .024v which is really should be .83. TPS is new and i have no idea what the hell is wrong.

When i move the arm on TPS i can get the voltage to go down from .024 to 0.

I have read that adding a dedicated ground to sensors ground terminal might help. I did that and the voltage jumped right to .79 but when i moved the arm on TPS the voltage just stayed at .79. I tried to drive the car like that and it would not shift out of frist gear.

What is going on? I really need your help guys. I always work on my cars and have built my turbo miata from gound up and now i feel like just bringing this jeep to a shop. I really dont want to do that.

Here is a little pic of my XJ. As soon as i fix this issue with TPS i will be installing a pacesetter header and borla exhaust.

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Anybody?

Hi! Welcome to !

Ok, need to know the transmission you have--AW4 automatic or AX15 manual? The TPS set values are different.

Thanks! I got a ax4 tranny.

You probably have an AW-4 automatic... the AX-4 was a 4 speed manual used behind the 4 cylinder 2.5L engines iirc.

Gee, I am an idiot. It is an aw4. I only have access to my iPhone right now and predictive textin sucks on it. Yes it's an aw4 auto with an i6 and Renex injection.

check out this site for Renix sensor info. It breaks them down pretty good as far as how to test and adjust if needed.
http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

magimerlin said:

check out this site for Renix sensor info. It breaks them down pretty good as far as how to test and adjust if needed.
http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Click to expand...

Yeah I got this site bookmarked and used the procedure to test the voltage. I figured that output voltage should be 17% of the input. So that means i my input is at only 3.5v I need to adjust tps to 0.59. Is I remember I still can only get it to be around .023 which is way lower. I probably have a ground issue somewhere. I hate electrical issues. Just can't stand them.

Here is a diagram of whats going on with the wiring in there. VC would be your 5v reference voltage and VTA1 the wiper arm is your output or signal voltage to the computer. And E2 is your ground. A quick test you might want to do is while its on put your meter on volts and put the leads accross VC and E2 ground and see if your dropping most of your 4.5V. And if its not put the leads while on from E2 at the sensor to ground on the computer preferably to see if your dropping excessive voltage on the ground side.

I hope that helps and doesn't cause more confusion. I hope you find the issue quick.

Thanks SFW516! I am at work right now and pics are blocked. I will try to remote into my Mac at home and see if i can take a look at the diagram.

man, that is confusing diagram. I take it its not a diagram of the square plug but the other one, right? That's another really confusing thing. Do i measure the volts on the squire plug or on the other one? they both have the same terminal letters on them.

If your input voltage is 4.5, then your TPS output should be 3.74V with throttle plate closed. If moving the TPS does not adjust the output then replace the TPS and adjust your output to 83% of your input voltage.

Yeah that's about what i get is 3.5-3.7 volts. I thought its 17% of the input value.

Ok. With the automatic you need to pull the four wire connector off the TPS. Turn the key to ON. Measure the voltage from "A", positive, to "D" ground. Make note of this--that is your REFERENCE voltage.

Now, reattach the four wire connector to the TPS. Key ON, back-probe the connector at "B", positive, and "D" ground. You need to adjust the TPS so that the voltage measured between "B" and "D" is 83 percent of REFERENCE voltage. If you can't achieve this value, replace the TPS and adjust again.

Back-probe of the connector can be achieved with small paper clips with one leg straightened out and stuck into the rear of the connector.

Good luck.

joe_peters said:

Ok. With the automatic you need to pull the four wire connector off the TPS. Turn the key to ON. Measure the voltage from "A", positive, to "D" ground. Make note of this--that is your REFERENCE voltage.

Now, reattach the four wire connector to the TPS. Key ON, back-probe the connector at "B", positive, and "D" ground. You need to adjust the TPS so that the voltage measured between "B" and "D" is 83 percent of REFERENCE voltage. If you can't achieve this value, replace the TPS and adjust again.

Back-probe of the connector can be achieved with small paper clips with one leg straightened out and stuck into the rear of the connector.

Good luck.

Click to expand...

Joe, is this a later revision of the procedure? The service bulletin I've always cited used the plugged-in voltage as the reference. It's been a long time since I worked on a Renix, and I doubt I'll need to again, but I wouldn't want to be dispensing obsolete information here, and I'll edit the paraphrase I usually copy and paste into TPS threads if needed. My 87 spat and hesitated if the output voltage was even a little high, but that might have been a quirk of that particular one, which was always a bit touchy about coming off idle quickly.

Matthew Currie said:

Joe, is this a later revision of the procedure? The service bulletin I've always cited used the plugged-in voltage as the reference. It's been a long time since I worked on a Renix, and I doubt I'll need to again, but I wouldn't want to be dispensing obsolete information here, and I'll edit the paraphrase I usually copy and paste into TPS threads if needed. My 87 spat and hesitated if the output voltage was even a little high, but that might have been a quirk of that particular one, which was always a bit touchy about coming off idle quickly.

Click to expand...

Right out of the FSM 90, Ignition section, TPS Auto trans test chart on page 8D-32.

Some people like to set the three wire side (like a manual trans vehicle) but I prefer to stick with the four wire side per FSM.

joe_peters said:

Right out of the FSM 90, Ignition section, TPS Auto trans test chart on page 8D-32.

Some people like to set the three wire side (like a manual trans vehicle) but I prefer to stick with the four wire side per FSM.

Click to expand...

Thanks. It appears that this did change, since earlier sources, including the 1988 service bulletin I have relied on up to now, tell you not to unplug at all. I'll make sure to note that change.

Unplugging allows you to measure the reference voltage as the ECU produces it / sees it. It uses it internally as the analog reference voltage for the analog to digital converter chips used to convert the sensor signals to something the microprocessor can understand. If there is a significant difference between the reference voltage with it unplugged and with it plugged in you either need a new TPS or have a wiring issue between the ECU and the TPS connector. Unplugging ALL the 5 volt reference sensors (MAP, temp sensors iirc, TPS, and HEGO? not sure on the last, don't know RENIX very well) should give you a reading of very nearly 5 volts on that wire.