Jeep wont move after 45mph, stalls, throttle position sensor? HELP

So I have a 1996 jeep XJ 6 cyl, 4.0, this problem has been happening for the past couple days and idk what it is...when I'm in drive, and get up to 45mph my jeep doesn't go anymore, it accelerates and the rpms go up past 3,000 but it doesn't actually move, I'm just coasting, but if I put it in 2 then I can drive past 45mph but my rpms goes past 3,000...so I basically can't drive on the hwy do you have any ideas?

It happens at like 35mph-45mph in drive, but If I turn my jeep on, put it in 2 it will never happen. But when I'm in drive and my jeep stalls at 45mph, I can throw it in 2 and it will drive like nothing happened...

Can anyone help me or tell me what this is, its extremely frustrating, and I need to get this problem solved as quickly as possible...

I"m no expert in the AW4, or automatic transmissions at all for that matter -- but the symptoms as you describe sound like you don't have 3rd gear engaging in your transmission. (I'm assuming 3000rpm is about when it would normally shift up into 3rd when in drive?)

first things first: does the tranny have enuf/the correct fluid in it? If so, I'd say you have a bad shift solenoid.

While the 3rd gear solenoid could be bad; there are other things that could cause this problem.
The TCU (Transmission Control Unit) could be going bad. It controls when the transmission shifts between gears.
Sounds as though you should locate a FSM (Factory Service Manual) for your year XJ to assist you in troubleshooting.

good call, i didn't think about the TCU.

CharlesS said:

While the 3rd gear solenoid could be bad; there are other things that could cause this problem.
The TCU (Transmission Control Unit) could be going bad. It controls when the transmission shifts between gears.
Sounds as though you should locate a FSM (Factory Service Manual) for your year XJ to assist you in troubleshooting.

Click to expand...

Where exactly is the TCU, and where would I buy one?

Thanks for the responses!

Search this forum for prior threads on the "AW4 Transmission"

https://www.google.com/search?q=nax...s=org.mozilla:en-US:official&client=firefox-a

And check out the treads on testing the Solenoids, #1 and #2, and and checking the TCU ground, and the fuse to the TCU.

There is no #2 on the shifter, there is 1-2, 3, and D. There are four gear ratios, 1,2,3 and OD.

Also you need to test the TPS, Engine off, power on, with an analog volt meter.

You can test the Transmissions hydraulics 1, 3 & OD shifting by pulling the TCU fuse. It skips 2nd gear, unless you hit about 4600 RPM in 1-2, or get to about 3000 rpm in 3rd and down shift, then it will go into 2nd.

Bad TPS, bad ground, bad fuse to the TCU, butchered wiring between the TCU and the Transmission case and bad solenoid are common and all easy to fix or replace. Solenoids, should have about 14 ohm resistance in the coil and can be tested at the pin outs that connect to the TCU.

Details on locations, pin outs, TPS testing are all here in dozens of older threads!!!

TPS needs to be ruled IN or OUT early in this process. Test or replace it. Don't futz around.
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The throttle position sensor is connected to the throttle shaft on the throttle body. It sends throttle valve angle information to the PCM. The PCM uses this information to determine how much fuel the engine needs. The TPS is really just a simple potentiometer with one end connected to 5 volts from the PCM and the other to ground. A third wire is connected to the PCM. As you move the accelerator pedal with your foot, the output of the TPS changes. At a closed throttle position, the output of the TPS is low, about a half a volt. As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be above 3.9 volts. Testing can be performed with an electrical meter. Analog meter is best. You are looking for a smooth sweep of voltage throughout the entire throttle band. While slowly opening and closing the throttle, take note to the movement of the voltmeter needle. There should be a direct relationship between the needle motion to the motion of the throttle. If at anytime the needle moves abruptly or inconsistently with the movement of the throttle, the TPS is bad

You should have 5 volts going into the TPS. At idle, TPS output voltage must be greater than 200 millivolts. At wide open throttle (WOT), TPS output voltage must be less than 4.8 volts.. The best is to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage. Move the throttle and look for smooth meter response up to the 4.49 at WOT.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.

The TPS is sensitive to heat, moisture and vibration leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following: -

NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics! It should be verified early in the troubleshooting process, when a transmission issue is suspected!

• Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".
• High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.
• Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.
• Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted acordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.
• Engine Misfire: A fault TPS can report values outside the deined acceptable range causing the ECU to incorrectly fuel the engine. This is noticable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.

I don't have a Analog meter, or any meter for that matter. I might just say screw it and buy a new tps...

What are the chances that my transmission is toast? That's worst case scenario...

W00GYB00GY said:

What are the chances that my transmission is toast? That's worst case scenario...

Click to expand...

Nealy zero. The AW4 transmission is very rugged, and most problems 99%, are a bad TPS, the chewed up wiring, dirty contacts in the wiring connectors, bad TCU fuse, burnt old fluid, or bad solenoid at the bottom of the pan in the AW4, which is real easy to test and replace, a 4th grader to do it, almost.

Well I don't have an analog meter to test my tps, would it just be a good idea to go to an auto parts store and get a new one, they are only $35 and it probably needs replaced anyways cause its stock...I really hope this is the problem though...

Sounds to me like you should start with a new TPS, they do wear out. Also shop for a multi meter ( and look on line for free instructions on how to use one) they are the most basic tool for debugging vehicles now days.

Sure, it could be something other than the TPS.

But it would be a crying shame to be chasing your tail when it might be that part. Test or replace it. The factory service manual will tell you to do the same. Gotta eliminate it from the equation as troubleshooting is a process of elimination. Finding out what it ISN'T is a good part of finding out what it IS.

And buy a meter. Everyone working on their XJ needs one. You can spend as little as $10 on them. WalMart usually carries an inexpensive meter. Personally, I like Equus and Innova for lower cost meters. Not as good as my Fluke, but they are pretty darn good.

I will buy a meter tomorrow and test the tps, then I will buy a new one if I need it.

But every single person I talk to tells me that my transmission is probably fked, and its getting me extremely stressed out...

When I get into 3rd gear in "D" my tranny basically slips like its in Neutral and my rpms go up, but I don't actually move, I'm just coasting. But when I'm in "3" I can move right threw 3rd gear like its nothing...I don't understand it.

I checked my transmission fluid and it was fine, I bought some Seafoam Trans Tune and put that into my tranny fluid to see if it would take out some moisture but it hasn't worked so far (I've only driven it for about 2-3 miles since I put it in.)

I'm just really hoping I wont have to replace the transmission because I hear that it's bulletproof, but then everyone tells me its probably screwed...

Have you checked the TCU fuse yet???????????????????????????????????????????????????????????????????????????????????????????????????

I couldn't find the tcu? I looked under the driver dash panel but found nothing, I think its in a different location for a 96'

Look under the passenger side kick panel, under the dash. It was there in 87-90, and may have still been there up to 96. But you may need to look under the hood for the main fuse box, for the TCU fuse in a 96? IN 87-90 the fuse was in a red wire in line fuse holder very near to the TCU, passenger side dash, lowest part of the dash - kick panel.

What exactly does it look like?