TFitzPat87

Hey Guys,

I've posted about my aw4 before, as I found out the PO was using AT+4 for trans fluid and my trans had some unfortunate slipping issues. I've since done a few (I think 5) drain and refills with Dexron III / Mercon, and I think it's gotten a little better, but still tends to slip when I get back on the gas at certain speeds. Like it should have down shifted, but didn't and when I get back on the gas it slips for a quick sec. Like it wanted to downshift, but was unsure and got stuck in between gears. I've adjust the TV cable already (pushed in button, pushed cable all the way in, released button, then WOT untill it ratchets out accordingly) but it still slips. It's not often, and not all the time.

I guess my question is, should I drop the pan to change the filter as well? I hear it's not really necessary, but my jeep did sit a bit before I bought it, and I wonder if theres just some gunk in there that needs to get out. I know these trans are solid, and with only having 71,000 miles, its hard for me to believe it's mechanically screwed up.

Sorry to ramble, but would love your thoughts, and to hopefully figure this out.

Crazy 8s

If it is slipping with still, you might have something damaged in there, or solenoids acting up.

The 'slippage' in your AW4 may not be slippage but the torque converter locking up or letting go. A misadjusted throttle position sensor will throw off the shift points and goof up the torque converter's lockup patterns.

TFitzPat87

Yeah, I'm wondering if I should just replace the TPS and see what happens. On mine the TPS doesn't need adjusting, but with the jeep sitting before I bought it, and me driving through a flood last August, it's possible its not working correctly.

If I accelerate consistently until I'm in OD, it shifts through the gears fine. It also seems to shift better after first start up, and then seems to act up a tad once its warm. I never saw any metal flakes or shavings when I did my drain & refills.

Again, it's intermittent and doesn't happen all the time. Most of the time, it shifts just fine, but at certain points it acts up on me.

tjwalker

If you do end up replacing the throttle position sensor, please do yourself a big favor and buy a genuine Mopar TPS from Jeep. Well worth the extra few dollars! Here's more on the TPS.
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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.

sycoglitch

+1 on Mopar sensors.

Also OP. You did adjust your TO cable right. Need to tighten back every so often

TFitzPat87

Thanks Walker. I think I came across that at some point. My Jeep is kind slow to come back to idle. Say I was driving home from work, stopped to get beer close to home, and then start it again 5 minutes later to come home... It's at 1250ish rpms, then takes a good 30 seconds (if not, longer) to idle back down to about 700. It shouldn't idle that high since its nice and warm, right? Not that it's real excessive, but I don't remember my old xj doing that. The more I think about it... I feel like its slow to come back to idle when I come to stop lights.

I'm starting to think maybe my TPS is a little stubborn, and just isn't that bad, it's just finicky . My XJ does run pretty damn nice, considering. I guess I'll need to get an analog multimeter, or just drop the cash on a TPS. Will definitely get one from Jeep though. Good project for tomorrow.

Thanks again.

TFitzPat87

TO Cable? What's that? I did adjust my TV cable. Slightly tighter shifting, but didn't change the minor slipping issue.

sycoglitch

stupid auto correct. Yup the TV cable.

Just to reiterate just to make sure.

1) depress grey button.
2) push plunger all the wAy in
3) release button
4) go in jeep and fully press accelerator and listen for clicking to know it was done.

TFitzPat87

Right, but I just twisted the throttle WOT from the engine bay.

sycoglitch

See, i use to do that too. Then i tried the accelerator peddle instead and the shifts felt tighter.