Transmission/ TPS help

OK, I have read what seems like a million threads about the AW4 and the TPS, yet I still cannot seem to fix my problem. I posted a couple of times...and I'm still not there. Having worked on this for the past few months without any success, I am going crazy and would be grateful for any help...

I have a 1988, 4.0, AW4, 231 on 35's with 4.56's (although I will be installing 4.88's as soon as I can find a little time). I have an 8.8 in the rear and although I put in a SYE, I have not changed the speedo gear, as the sppedo is not far off (checked against GPS). The rig is not shifting right, as it seems to be missing a gear and my mileage has dropped from around 17 to 10 at best.

If I put the rig in Drive and take off, it doesn't seem to go into first, as it is sluggish and shifts quickly into what seems like 3rd. Then, it will quickly shift into what I assume is OD. The transition between 3rd and OD is almost unnoticeable. If I am climbing a grade, I have to have the gas pedal slammed to the floor to keep moving and it usually won't downshift on its own.

If I shift manually, the rig will start out in 1st, and it (of course) has way more torque. I don't get 2nd and when I put it in 3rd, it goes. Again, if I switch between 3rd and OD, the difference is very slight and barely noticeable. If I manually downshift from 3rd to 1-2, sometimes it seems to go into 2nd, and then it will lock up into 1st and not come out until I manually put it into 3rd. Again, the torque is very distinguishable between taking off with it manually in 1-2, and taking off in Drive. This is why I don't think it is going into first when the tranny is in Drive.

I changed the TPS, although I am confident it is not properly adjusted. I tested the wires at the square quick connect. One wire stays at a constant (yet approximate) 4.5. The other, which according to the posts I have read, should "sweep" between 0.5 and 4.2. I cannot get these readings to save my life. If it is set at its lowest of 1.5, then it will only go as high as the 3.5-range. If I get it up to the 4.5 range, then the lower only drops into the 2's. Note, I only have a digital meter, so that is what I have been using. If someone can answer, why would analog read any different?

I also have heard there should be two adjustments, if so, how do I do it and what are the settings, the order to do it, etc.?

Other factors...I am using Royal Purple synthetic trans fluid and it is full.

I have an outdated O2 sensor, and although I can understand how that might effect mileage, I don't see how it would effect shifting. Please correct me if I am wrong.

My knock sensor broke off when I changed engines a year ago and I have never hooked it back up. Could this cause some grounding problem or other?

A while back, I was having problems with the NSS not letting it start. I pulled it and cleaned it.

Sometimes, when I put the selector in Park, it will not lock and I will have to run it back and forth a couple of times to get it to lock into place.

I also had problems with the starter relay not wanting to work. I bypassed it with a "bump" switch. Around this NSS/ SR problem is when I started having the shifting problems. Tonight, I hooked the starter relay back up with no help, but now when I start the vehicle, the RPM's are extremely high and pressing on the gas pedal does not correct it (this was after taking it for a ride too).

The TCU fuse is good and I have pulled it and attempted to reset the TCU.

I have also changed out the CPS, although that shouldn't effect shifting.

I assume the problem must be electrical, since the tranny acts right so long as I shift mannualy (also considering how many other electrical problems the rig has had recently). I am not very electrical savvy. I can fix electrical problems, but I am not good at identifying them at all and have no sense of "oh yeah, it might be that", like I do with mechanical problems... If any of you are electrical wizards, I would sure like to be pointed in the right direction.

If anyone can help me figure this out, I would be grateful. I''ve spent a ton of money building almost every component of this rig, but it is all moot without it shifting right. Thanks in advance for your time and help.

Kevin

you need the knock sensor. It retards the timing or is part of the retard process important on the renixes.
how to check here, but sounds like you need to jusst replace yours,

http://www.jeepforum.com/forum/showthread.php?t=6066

Kevin,

Same problem here and seems common on other forums as well. So far I've changed fluid, filter, TCU, TPS & 10A fuse.

Hopefully one of us will solve this soon!

I'm still reading up trying to understand how the AW4 works.

This might be helpful if you haven't already found it.
http://jeepgarage.free.fr/OWN/auto%20trans%20diagnosis.pdf


Steve.

I had some of the same transmission problems when I bought my 1988 Jeep Cherokee Pioneer.

I found this link to be quite helpful to start my search for the cure.

http://www.transonline.com/transdigest/magazines/1997-10/Shift%20Pointers/index.html
(I don't know if you have found it before .... but it is worth bringing up again for others to see.)

At first I tried to use a analog meter.....mine was not accurate enough to get the readings. Mine was only good enugh to tell If I had current or not.

Then I borrowed a DVM ....I could not get proper readings (consistently) there also because of a faulty probe on the meter.

Once I established that I had a good DVM reading I went to work using the steps in the link I posted.

I worked my way thru the whole process as the link suggested...and with the help of Ecomike (Thanks again) found my problem to be a cut wire (red one from the TCU) to the TPS.
From what you have posted I would say that your TPS is faulty. You only mentioned that you changed it....not if it was new or a used one.

Until you can get the proper readings to and from the TPS and TCU you will not get the thing to work correctly (that was my case anyways).

On a side note:
If you unplug your TCU completely you can pretty much tell if your problem is electrical or mechanical.
When unplugged you should be able to shift thru the gears manually. If so then the link above will help you (hopefully) pinpoint your problem.
Also make sure you have good ground points from the battery to the engine and chassis.

Good luck on your hunt for the problem.....

Ok, I ran the test procedure from the link Steve sent. Everything checks normal except the following:

C-3 (speed sensor) = 0.01 volts...............It should read 5 to 8 volts.

C-9 (shift lever in Drive) = 0.01 volts..........It should read battery voltage (approx. 12.25 volts).

C-10 (brake sensor) = 12.06 volts with brake on and 12.76 with brake off.....It should read 0 volts with the brake off and battery voltage with the brake on.

D-2 (TPS voltage input) = 0.05 closed and 0.05 with the throttle wide open...... It should read 4.5 closed and 0.5 wide open.

Where do I begin??? I assume I should set the TPS, but I cannot seem to get it onto spec. Could somone please walk me through doing this.

After that, where is the speed sensor and is it an easy fix or something to try to clean, such as the brake sensor? Also, how do I fix the voltage when the shifter is in Drive, or will the other things correct this?

I don't know if it makes any difference, but when I adjust the new TPS anwhere from the lowest setting, sometimes it will rev extremely high when I start it, especially after running it for a while...

Thanks for your help.

Kevin

Alright...thanks to MiNi's help, I got the TPS dialed in. Strange thing is that although it reads right at the connectors under the hod, it still doesn't read right at the TCU input connector. What a difference having this dialed in...it is like a whole different Jeep (but it is still not 100%). The brake sensor and speed sensor are still not even close to reading right. Any direction on these?

Thanks again!

Kevin

sweeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeet :gee:

kj139 said:

What a difference having this dialed in...it is like a whole different Jeep (but it is still not 100%).

Click to expand...

Makes ya feel good when something starts to work correctly. :clap:
I bought my XJ with the mindset of replacing the transmission......what a relief to find it was only a cut wire.

kj139 said:

Alright...thanks to MiNi's help, I got the TPS dialed in. Strange thing is that although it reads right at the connectors under the hod, it still doesn't read right at the TCU input connector. What a difference having this dialed in...it is like a whole different Jeep (but it is still not 100%). The brake sensor and speed sensor are still not even close to reading right. Any direction on these?

Thanks again!

Kevin

Click to expand...

If it's shifting at all, the speed sensor is fine. On the brake sensor, try cruising at a steady speed and then tap the brake with your left foot. If the rpms jump a bit it's fine (that'd be the t/c unlocking). If it doesn't you can cleanup the switch fairly easily. It's located high up on the brake pedal. Below is something I wrote on this previously

lawsoncl said:

It's not too hard to remove the switch and clean it. You just have to be part contortionist to get to it. :} The metal bracket that holds the switch has a screw on the right side, facing the passenger side. I think it had a 1/4" hex hex, but I'm not real sure. You'll probably have to find it by feel but it's right behind the stamped M in the bracket on mine. If you take out that screw the bracket will slide to the right and come off. That's easier than trying to unscrew the switch from the bracket and having to get it back in the same place. The switch itself can be popped apart by carefully pressing in the little tabs on the side. Here's what the switch looks like (part of the bracket is missing).

Click to expand...

Outstanding. I'll clean the brake sensor tomorrow and it's good to know I don't need to change the speed sensor. Any thoughts about the voltage problems at the TCU input?

Thanks again guys...There is finally light at the end of this tunnel!

Kevin

On the Renix setup, the wires from the square connector on the TPS go straight to the TCU connector, so if you're not getting the same measurements at either end then the wire may be damaged? You measuring at the square connector which is for the TCU, and not the flat one that is for the engine computer?

You are measuring these voltages with the TCU plugged in and the key-on right?

lawsoncl said:

On the Renix setup, the wires from the square connector on the TPS go straight to the TCU connector, so if you're not getting the same measurements at either end then the wire may be damaged? You measuring at the square connector which is for the TCU, and not the flat one that is for the engine computer?

You are measuring these voltages with the TCU plugged in and the key-on right?

Click to expand...

Yes to both questions. I set it up under the hood on the square connector, but at the TCU input connector, it is very different. I will follow the wires tomorrow to see if there are any problems visible.

Thanks!

Kevin

I've been busy too. Thanks to B.Raider for that link which is very useful and easy to follow.

My results:

I didn't get battery voltage on C8 & C9 with the shift in 1/2 and D, but battery voltage at each when the shift is in another position.

For the solenoids, I get 7 ohms instead of 11-15 except Solenoid 1 where I can't get a resistance reading at all!

Otherwise, at D2 the TPS pin, i get 4 open and .9 closed which is the opposite of the table.

So, I think I have a problem with Solenoid 1 or the connection to it. Yep we seem to be getting somewhere.

Steve

Kevin,

The speed sensor is a pulse of 5 - 8 v each revolution. So presumably as it rotates it varies from 0 - 6 v or whatever. I didn't get a reading on C3 until I started the engine and than got about 6v.

Steve.

Ok, after a bunch of driving, it has much better throttle response, and it will shift fine in any of the other settings except for Drive, where it still doesn't seem to take off in first. It seems like it is taking off in 2nd, but I guess it could be 1st and then no OD; however, the 1st gear in Drive is nowhere near as tourquey or low-geared as if I manually put it into 1-2. I am wondering if the Knock Sensor could be putting it into "limp home" mode, thus causing it to take off in other than first gear. Or could the brake sensor cause this?

Any thoughts???

Have you not replaced that knock censor yet? I told you you need that on those renix version engines.

Not yet...I can't find anyone who sells the old type.

Junk yard

I think your problem with first gear is the shift solonoid. My 96 did the same thing, it would not pull out in 1st gear in drive but would if I pulled the lever down into 1-2 it would pull out in first gear. I can't remember which solonoid it is(there are 3) but they are easy to get to and replace, just pull the pan and filter.

I would try to find one in the junk yard before popping $100-150 for a new one.

I dis agree with Mini Beast, you do not need the Knock Sensor on the RENIX, it was deleated on the 91+ models. I have been running with out a Knock Sensor for 2 years now and no issues. You do however need to make sure that your engine is tuned good, run good gas and all sensors are working as they should. Also make sure the wires are not touching where the sensor or wires broke off at, that would retard the timming. That circuit needs to remain open if it is unplugged.