mitch500

Hello,

My 1996 jeep XJ 4.0 AW4 4X4 won't shift down when I come to a stop. It feels like its starting in 3rd gear. It's really slow to get going and once in get my speed up I can feel it shift to 4th and I have power once I get my speed up.... When I come to a complete stop and I put the gear selector into 1-2 I have plenty of power as its starting in first, I then can manually shift the automatic lever to 3 then I drive...

I have adjusted the TV cable according to the sticky. I also read it could be the TPS and or solenoid/govenor pressure switch... Maybe someone can chime in with a remedy?

Thanks,
Mitch

tjwalker

1. First, verify that transmission fluid level is correct on the dipstick, with a hot engine, fully exercised transmission.

2. Is fluid RED in color? If not, change it!

3. The throttle position sensor is directly involved with shifting characteristics of the AW4. Here is more on this very important sensor.
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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 accordingly 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 denied acceptable range causing the ECU to incorrectly fuel the engine. This is noticeable 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.

mitch500

1. Yup just changed it this summer. Also checked it today with a warmed up jeep in nutral and running. It is at the max mark.

2. Nice and red. Not brown or burnt

3.i will check the TPS... Although I only have a digital multimeter...

AndrewK

Did this ever get solved? I'm experiencing the same exact symptoms. Just flushed my ATF and planing on replacing the TPS asap.

mitch500

Yes. After replacing TPS and the transmission control unit with no success I took the trans oil pan off and replaced the shift solenoids. It was shift solenoid 1-2 that failed.

Kalali

So how difficult would it been if you had shared the outcome for everyone to know.....

AndrewK

Not the outcome I was hoping for :/

mitch500

Not sure what your getting at bud. I shared.

Chris Lippold

thanks man. My truck has exact same problem. I already changed the 1-2 spellbound but i guess i should check it again