Sudden problem with aw4 shifting

1990 renix 4.0/aw4
So last week I had a high idle problem. I found the source. It was vacuum lines disconnected on the intake

Yesterday, feeling good about the jeep. I decided to drive it to work.

I made it 1 mile before something went crazy. Trans would not shift or engage any other gear then 1st/second. If I redlined 1/2 and popped it into 3rd. It acted as neutral.

I left it in 1/2 and limped it home

Today I warmed it up for 30mins idling. And checked the fluid. It's right where it should be and color is spot on. (Clean!).

It does have a minor pan leak (not enough to make driveway spots).

My renix buddy thinks its electrical. I've been fighting the electrical in this jeep. Everything works but wipers/headlights and stereo at the same time brings the volt gauge almost into the red (8-10v). I've added one extra ground. And all battery cables are new. 4/ga parts store specials. Battery is a brand new orbital xcd.

Where do I start???

Check the inline fuse, under the passenger side kneeboard, for the TCU. That's acting like the TCU is not working.

Loss of TCU fuse would not do that. He should get 4th in D, and 3rd in 3, with out the TCU. Sounds like the shift linkage has come loose to me.

In fact pull the TCU and shift manually, if it all works then the TCU may be bad, otherwise it is linkage or the AW4. If it works with the TCU fuse pulled, the problem may be the TPS or the TPS ground. Both are common problems with Renix jeeps.

Ecomike's plan is best, unplug it and see if it drives shifting manually. If it does not, you need to check a few things - throttle valve cable, shift linkage alignment, etc. It will be missing 2nd gear and won't have TQ lockup but should get OD in D, 3rd in 3, and 1st in 1-2.

If it shifts normally you have some electrical debug to do.

kastein said:

Ecomike's plan is best, unplug it and see if it drives shifting manually. If it does not, you need to check a few things - throttle valve cable, shift linkage alignment, etc. It will be missing 2nd gear and won't have TQ lockup but should get OD in D, 3rd in 3, and 1st in 1-2.

If it shifts normally you have some electrical debug to do.

Click to expand...

X2

My money is on a bad TPS or TPS ground. It has two separate halves, and separate grounds!!! The square connector side talks to the TCU for shift timing!!! The TPS and calibration details are here.

http://www.naxja.org/forum/showthread.php?t=1080172

TCU is the yellow box attached to the lower dash (aka knee board)??

The yellow box is your cruise control, TCU is on the passenger side, in about the same place.

FYI, if you're having other electrical issues, that might be an important thing to solve before you start pulling wires on the TCU. Clean the battery terminals, and depending what kind of terminals you have, take off the clamps that hold the wires on, and clean the wires/clamp area. If that doesn't solve your low-voltage problems, the main power wire off the positive should lead to a distribution relay that is about 6" behind the battery... clean that, and so on.

You might also want to do the same thing with the grounding cable, as those frequently get all grungy.

Battery, cables, everything is new and very clean


I am checking the options listed, today

Start here:

Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011

Do this, too:

Cruiser’s Trans Plug Refreshing

Over near the transmission dipstick tube are 2 rather large connectors. One is black and the other gray. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.
Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.
　
Additionally, if your Jeep is an 87 to 90 Renix, it’s always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While you’re there, find the fuse right in that area for the TCU. Remove it and spray out it’s receptacle and clean any corrosion from the fuse.
Revised 9-10-2012

And when it comes time to check the "trans" side of the TPS, use this:


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: With the Key OFF, and 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 only a flat three-wire TPS mounted on the throttle body and it provides data input to the ECU. It 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. Loosen both T-20 Torx screws attaching the TPS to the throttle body and rotate the TPS until you
have achieved your desired output voltage. Tighten the screws carefully while watching to see that your output voltage remains where it is supposed to be. If you can't achieve the correct output voltage, replace the TPS and start over.
Sometimes, after adjusting your TPS the way outlined above, you may experience a high idle upon starting. If that happens, shut the engine off and reconnect your probes to B and C. Start the engine and while watching your meter, turn the TPS clockwise until the idle drops to normal and then rotate it back counterclockwise to your desired output voltage.
AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs have 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, as outlined above—FOR ALL 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. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY. 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.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES: Check the square four-wire connector side of the TPS.
If you have ENGINE ISSUES check the flat 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 09-22-2012

Bump: After a week I have cleaned the block ground. Checked the fuse for the TCU. And verified the TPS was plugged in

I started the jeep tonight for the first time in days. It's cold outside (45*). And after 10 seconds of cranking it fired and immediately idles at about 500rpm. I think I have multiple issues.

Meanwhile. I tried to drive it with no change in shifting. 1-2 and then nothin.

So all you did was the engine block dipstick tube stud ground?

Why not the rest of it? TPS test? Trans connectors?

cruiser54 said:

So all you did was the engine block dipstick tube stud ground?

Why not the rest of it? TPS test? Trans connectors?

Click to expand...

That's what I am stating. I will be following thru to the next phase and cleaning all connections and trying to test for ground.

Meanwhile I am going to purchase some 2ga wires from a local shop and add some additional grounds.

If you pull the fuse for the TCU (or pull the harness), it should drive like a manual. With it off-line, you'll need to start in first and then shift up but at least it will be drivable. This would also narrow down if it's TCU related or something else. The speed sensor can also go on you. That makes the TCU think you are moving so it keeps the trans in first (letting the RPMS go way up).

Bump 4 months later i finally pulled this xj out of storage and tossed a new TPS at it! its running great and shifting right!

TPS was the issue!