2000 XJ 4wd AUTO - Stumbles when accelerating but ok when TCM removed and shifting manually

[FootHillsXJ]

2000 XJ - 153,000 miles - Been trying to pin this one down using a bunch of internet resources but I need some direction. So when I am accelerating up hill, my XJ gets confused and starts bucking/hesitating. It doesn't do it when I am just cruising on residential streets. It is just when I am at highway speeds starting up an incline and I give it gas to keep my speed up. If I put the pedal on the floor, it clears up and I can accelerate smoothly. After reading a lot on some forums and pulling a P0700 code, I decided to yank the TCM. I can drive around up hills and all over shifting manually and there is no hesitation or bucking. I installed a junkyard TCM and the problems started up again exactly the same as before. Any ideas on where I need to look next. Thanks!

 

[75SV1]

First, lift and tires? Also, header, 2.5 catback?
Next the AW4 is controlled by 5 different inputs. Maybe more. TCU, EMC, TPS, Brake Light sensor, and NSS or also called Range Selector in '98 and up. I would guess TPS (Throttle Position Sensor). Possibly a dead spot in it. Still best to test. Use only a Factor MOPAR one. There are a few threads on AW4s.
Another possibility, if you are lifted, and header, and 2.5 exhaust. The Throttle Body in to restricted. I had this issue with even 31's, Doug Thorley header and a 2.5 catback. I forget the name of they guy selling the Catback. Also, had some other stuff, like plugs and ignition wires. I also have an IRO Catback on my 2000 XJ.
The Throttle Boby (TB), I ran a stock one and had issues with shifting on inclines. I bore it out to 60mm through. Just taking out the lower restriction. I didn't have shifting issue on the same inclines. I did go with a 62mm later. It didn't run as good. I have the 62mm on the 2000 XJ with a mini-stroker. It seems to run good. Another thing with the TB, might be the shaft seals are out. I rebuild built and bored about 5 TBs. Some of the shaft were worn. The 'orings' were brittle and dirt had gotten into the roller bearings. I clean, regreased, and replaced the orings. I gave a few to a guy who works on Jeeps etc. Seems to like them.

 

[FootHillsXJ]

First, lift and tires? Also, header, 2.5 catback?
Next the AW4 is controlled by 5 different inputs. Maybe more. TCU, EMC, TPS, Brake Light sensor, and NSS or also called Range Selector in '98 and up. I would guess TPS (Throttle Position Sensor). Possibly a dead spot in it. Still best to test. Use only a Factor MOPAR one. There are a few threads on AW4s.
Another possibility, if you are lifted, and header, and 2.5 exhaust. The Throttle Body in to restricted. I had this issue with even 31's, Doug Thorley header and a 2.5 catback. I forget the name of they guy selling the Catback. Also, had some other stuff, like plugs and ignition wires. I also have an IRO Catback on my 2000 XJ.
The Throttle Boby (TB), I ran a stock one and had issues with shifting on inclines. I bore it out to 60mm through. Just taking out the lower restriction. I didn't have shifting issue on the same inclines. I did go with a 62mm later. It didn't run as good. I have the 62mm on the 2000 XJ with a mini-stroker. It seems to run good. Another thing with the TB, might be the shaft seals are out. I rebuild built and bored about 5 TBs. Some of the shaft were worn. The 'orings' were brittle and dirt had gotten into the roller bearings. I clean, regreased, and replaced the orings. I gave a few to a guy who works on Jeeps etc. Seems to like them.

4.0, 4 in lift, stock exhaust with fresh cat and muffler. I did get a TPS sensor code a while back that was high voltage to TPS. I replaced it because it was getting 3.5V at WOT. Funny thing is the NAPA replacement is also getting 3.5V.

 

[Unclewolverine]

I've had 2 tps's bad straight out of the box.

 

[lawsoncl]

Possibly a bad tps or the t/c solenoid is acting up. Test the ground wire at the sensor as well. A bad ground will make it read high.

 

[Tim_MN]

Did you test the O2 sensors? The O2 sensors are NTK, and NOT Bosch or no-name generic?


TPS failure may have one or more of these Physical Symptoms:

1) The engine loses power and is stalling.
2) The engine will idle, but may die as soon as you press the gas pedal. When driving, it seems as if all power is gone.
3) Sometimes it feels as if the transmission is failed or isn't shifting properly, if at all. If you quickly jump on the gas you might be able to get the transmission to shift, but it won’t shift properly by itself. Shifting manually, the transmission goes through all the gears.

NOTE: The Throttle Position Sensor (TPS) is DIRECTLY involved with transmission shifting characteristics.

TPS TESTING

The TPS is mounted on the throttle body. The TPS is a variable resistor that provides the Powertrain Control Module (PCM) with an input signal (voltage) that represents throttle blade position. The sensor is connected to the throttle blade shaft. As the
position of the throttle blade changes, the resistance of the TPS changes. Along with inputs from other sensors, the PCM uses the TPS input to determine current engine operating conditions. In response to engine operating conditions, the PCM will adjust fuel injector pulse width and ignition timing.

The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. The PCM receives an input signal voltage from the TPS. It is best 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. This will vary in an approximate range of from .25 volts at minimum throttle opening (idle), to 4.5 volts at WOT wide open throttle.

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:

• 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 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 excessive misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.


Cheap crappy Chinese "Lifetime Warranty" parts are often out of specification or even failed right out of the box. Many times they have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep sensors.

 

[lawsoncl]

4.0, 4 in lift, stock exhaust with fresh cat and muffler. I did get a TPS sensor code a while back that was high voltage to TPS. I replaced it because it was getting 3.5V at WOT. Funny thing is the NAPA replacement is also getting 3.5V.

You either got a bad one out of the box, or I'm betting the ground to the sensor is bad. The ground wire attaches to the stud over by the oil dipstick. It's never a bad idea to pull that apart and clean up all the grounds.