We're talking 87 to 90 4.0 Renix Jeeps here. Different animal.

 

RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned. It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION: RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body. This manual transmission vehicle TPS provides data input to the ECU. The manual transmission TPS has three wires in the connector and they're clearly embossed with the letters A, B, and C. Wire "A" is positive. Wire "B" is ground. Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors. Note the voltage reading--this is your REFERENCE voltage. Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts. Adjust the TPS until you
have achieved this percentage. If you can't achieve the correct output voltage replace the TPS and start over.
AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs has a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles—
FOR ENGINE MANAGEMENT RELATED ISSUES. However, the automatic TPS also has a square four-wire connector clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage. If you can't, replace the TPS and start over. So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU.
If you have TRANSMISSION issues check the four-wire connector side of the TPS.
If you have ENGINE issues check the three-wire connector side of the TPS. For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 04-08-2012

 

whoop...sorry... missed that part....

 

No biggie.

 

mine is having similar problems. seems to be only when it is hot and it is no consistent and no power till 3000rpm, got told today to look into the map sensor. not sure if this is true but it was a mechanic that suggested it and he was not selling me anything so i would like to think it is good advice. anyone else heard of this possibility? if so it might help you out

not trying to hijack this thread, but might be beneficial to a few of us.

 

just realized mine being a 93 might be acting differently differ4ent systems. sorry if i was wrong there

 

Yea, they changed allot between 90 and 91. You can still check the little tube from the inside of your TB, back up to the MAP up there on the firewall. That's gotta be perfect. You can pull the little deal off the MAP and check the end for vacuum with your finger.

Wonder what happened with eriejeep?

 

The above mentioned is all good. However, with the stalling and backfiring issues one other thing in the 4.0: The CPS.
It will fail, at some point, during its life and all those symptoms can well be related to it. Multiple threads on those. Replace it with a good quality one and chances are issues of stalling/backfiring are gone. And if not, one less thing to worry about in the future (cause the CPS will fail at some point).

 

Excellent advice.

 

On YOUR CPS, I recently found this link on testing the later, OBD II CPS, which may well apply to yours. I haven't tried it, don't know anyone who has. It looks like he's verifying XXXa volt, (XXXXXXXXX Mil.Volts), presumably AC, (with a true RMS meter), (back-probing, with it connected), at his third (Red) wire. (not the ground, and not the 5V-DC sensor feed). I don't know what % difference I would expect from my "cheap-o-meter", as opposed to the true RMS, but it might not be much. (about 4-1/2 minutes into the firse Vid, IIRC) http://www.cherokeetech.com/VBull/sh...agnosis-Videos

 

i have seen the cps cause it to stall, and in most cases stop you from being able to start. i habve yet to see one cause backfireing(could be i have not been doing this long enough). and the hesitation at low rpms is not something i have seen first hand that was caused by the cps either.

 

Theoretically it could happen if the sensor was putting out a signal just strong enough to run and dropped below that range intermittently or was just barely barely strong enough.... Get something long and a hammer and give it a few light whacks to get it slightly closer to the flywheel and see if the problem goes away..... Did this on my buddys xj and its been running for 3 weeks..... Probably should get around to installing the new one.....

 

Pretty slick, slick! It looks to me like those things are capable of almost anything.

Optimus, (I have an Optimus, stove btw), check your "wireing down under", make sure your 02 sensor wires are not grounding or shorting. When my renix was backfiring, I had wires grounding. Not sure which, We Renix guys have more stuff down there.

 

im in a 93 so i dont think it is a renix. will check into thoes wires. and make sure they are not shorting on anything. might be another place for me to check out. new coil/wores plubs and distributer had cleaned it up for about a month of city use. not sure what new started its fit on me again . thanks for the tip tho

 

Ha! perfect example of a thread getting confused. So you are not stalling. You might start a new one so guys familiar with your year will be more likely to check it out. Good luck! I'll part with this>>>>>>

Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep.