I'm finishing up my 86 mj project. Its an 86 with a 95 donor 4.0 engine, aw4, wiring harness and dashboard. The thing is I can't get the thing to shift when I drive. If I pull the fuse I can shift it manually. When I test the tps it has a slightly high voltage at idle but otherwise smooth curve as I turn it and normal voltage at wot. I've replaced just about every sensor on this thing. The other issue I have is that on start up it idles at 1k for half a second, then falls on its face at 750ish ripppums until the engine heats up, then it idles fine. Im sure that the tps is bad but I've replaced it twice and I'm getting good results on the meter. Any suggestions before I pay a mechanic to chase his tail? Any help would be apreciated.

 

It''s not your TPS. It tests fine and you've replaced it twice. Quit fixating on it or you'll never find the real problem.

Check your wiring. Also your transmission computer is suspect.

Check for vacuum leaks for that idle issue.

 

I dont think its vacuum because if I unplug the tps and start it, there's no falling flat on its face. It just runs very rich at that point. I went to change out the speed sensor today but bought the wrong one (different connector). If that didn't work then its time for a new tranny computer. Is there any test for the wiring or the tranny computer that you can think of?

 

I recall the throttle switch is adjusted, ignition on, with throttle closed, You need to set it like that, per the factory specification. dont concern yourself with its voltage at other positions for settings, set it when closed.

when you say it wont shift when the engine is running, do you mean it wont go out of park? what gear if any works?
also do a vacuum test, it can be very revealing, it is a simple fast test, no reason not to do it. A vacuum test really helped me solve an idle issue on my 90 renix jeep. Just do it, it is very sound advice, if it is good, then smile, if it is bad, smile, you found a problem that needs to be addressed. A vacuum test is smiles all around. dont tell me you dont like to smile!☺☺☺☺☺☺☺☺☺☺☺☺

 

I believe that 95 tps' are non adjustable. My mj/xj hybrid will go into reverse and drive just fine. But will not go into second gear and won't go over 30ish mph. I can definitely try a vacuum check over the long weekend though.

 

What year AW4, trans computer, and TPS sensor? There are some compatibility issues. The Renix era trans computer needs the dual output TPS sensor, because it expects the voltage to run from 5->0 volts which is backwards from the input to the engine computer. The later year trans computers are normal, and use the same input signal as the engine computer. Second issue is the rear speed sensor change along the way in 98. I'm pretty sure the 95 AW4 output speed sensor is still a magnetic switch that closes once per revolution, which you should be able to check with a volt or ohm meter.

 

The aw4 is also a 95. I took it out as one piece from my old parts jeep. The tps has only one pigtail unlike the remixes two. The speed sensor that i got, fit into the transfercase but the connector was a 3 blade while my connector was a 3 bullet style lol. Yesterday was one kick in the teeth after another.

 

The trans computer uses two inputs to determine when to shift. The TPS and the rear output speed sensor. If the TPS says you're wide open throttle, or the rear speed sensor isn't firing. If you're not hitting 2nd, then it could also be a bad #2 solenoid.

So all 1995, including the trans computer then? In other words, you're not feeding a 0-5 volt TPS signal to a renix rtrans computer that wants 5->0 volts. I double checked, and the output speed sensor in the tail of the trans (not the vehicle speed sensor in the xfer case) is the same part from 87 to 97. Not sure where you came up with a 3 pin part, as both the earlier and last sensors only have 2 pins. I know the older 87-97 sensor will not fit the 98+ transmission - it's too long and hits.

On 87-97, the wiring to the output speed sensor should have +12 or +5 volts (that changed with renix to HO I think), and get pulled down to zero once per revolution as a magnet on a rotor inside the trans passes by the sensor/switch. Jack up a rear wheel so you can turn it by hand which will turn the transmission output shaft, and put the meter across the sensor and watch for the voltage switching back and forth.

The 98-01 sensors generate a/c pulses 4x per revolution instead of opening closing a switch. For those, you'll get better results by measuring the sensor for a/c voltage with the xfer case in neutral, trans in drive. From my previous testing, the voltage spikes from the sensor while unplugged gets up to 30+ volts at 3000 rpm.

 

I'm attaching two pictures. The first is the rock auto I bought and the second is a picture from a similar thread of what I have. Rock auto says they may require an adapter harness and half of them come with a new pigtail. Im guessing mid year change had one and later ones had a different. I also found out I can get the harness at orileys so I'll stop on my way home. I believe 95's only had one sensor as opposed to later models that had two. The odd part is that my speedometer works fine and I believe older jeeps like this 95 ran this sensor to the computer and the speedometer. If its not the tps or speed sensor does that leave just the computer and wiring. I also ohmed my solenoids earlier and I believe they all read 13ohms. They shift when I pull the fuse and shift manually. I aprecaite all the help from everyone!

 

Did you plug in the transmission controller? It's under the dash, essentially by your right knee from the driver's side.

Assuming you did that, you can use a bent paper clip to back probe the connector to check voltages at it. See if it's getting the TPS voltage at the connector to the TCM. You might need an oscilloscope to check the output speed sensor signal to the TCM. Other than that, check +12v and ground points, and you can also check the resistance of the shift solenoids from that connector as well. I know you already tested them, but this will tell you if you have an issue with the harness.

 

Those pictures are of the vehicle speed sensor, which plugs into the xfer case if you have 4wd. That is NOT the sensor that the transmission computer looks at. You want to look at the output speed sensor on the transmission itself. See the picture (ignore the extra input speed sensor, since the picture is from a 98+). Look in front of the xfer case, behind the mounting plate for the xfer case linkage.


He must have plugged in the trans computer if it's starting in 1st gear in (D). On an MJ, the trans computer would be passenger side behind the trim. Not sure where he's got the trans computer mounted since he's transplanted wiring from a 95 (assuming it's a 95 trans computer too)

 

Did some poking around, went for a test drive and it magically started shifting. I either made a connection that wasn't tight by unplugging and plugging everything in, or something was frozen from sitting for years and unfroze. That or its an intermitten problem and it fixed itself for now and ill be back here in a week when it unfixes tself lol anyways thanks for the responses!