Torque converter...? I have some AW-4 problems -
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post #1 of 3 Old 06-09-2013, 08:08 AM Thread Starter
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Torque converter...? I have some AW-4 problems

I have some transmission problems. Got a 98 xj sport auto with the 4L. A couple months ago a noticed a rattling/clicking/slight grinding noise coming from the bell housing area but only in R or one the drives. After a few weeks it wouldn't downshift at stops so accelerating was really slow as if still in 3rd. And after 20+ min of driving would start to leak a bit. Soon realized the only sure thing I had was 1st gear in D1/2, 3rd in D3 and 4th in D. But other gears randomly work and now it's steady where I need D1/2 to start my drives and I shift into D3 and that gets me where I'm going after that. I changed all fluids and trans filter a month ago and noises subsided but the shifting problem is still there. I'm low on funds so don't wanna replace unneeded parts. Can someone give me a sure answer? FYI there's 250 k miles on this thing and engine runs like a top.

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post #2 of 3 Old 06-09-2013, 08:11 AM Thread Starter
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I posted in another area and was told I should do it here. I have stopped driving it and was given the trans manual link but figured it was worth a shot to see if someone has had the problems before. I appreciate the help.
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post #3 of 3 Old 06-09-2013, 08:31 AM
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The two issues may be related or not. A cracked flexplate or loose flexplate bolts will make noises. Use the Google, find out how to check the flexplate bolts.

A faulty Throttle Position Sensor or failed transmission solenoids may the cause of the shifting problems. See the TPS testing info below.

Go here ( ) and find the AW-4 Transmission Service and Diagnostics Manual. Follow the troubleshooting info.

A good used AW-4 transmission will be 1/4 the cost of a rebuild.

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 is also DIRECTLY involved with transmission shifting characteristics. The TPS function should be verified early in the troubleshooting process, when a transmission issue is suspected.


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 4.8 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 faulty 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.



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