jon with the jeep

hi i have a 96 xj country w 190,000 and an automatic transmission. my problem only occurs about half the time i drive. ok so here it is when im doing 45 or better and take my foot off the gas it winds down in that gear and wont downshift. i have to tap the brakes to get it back to third so yea its kind of annoying. i have owned this cherokee for 5 years now and wouldnt trade it for anything. i have done a lot of maintnence repairs and extrasand this is finally my last repair and ill be good to drive like a normal person again. please help what should i do?

tjwalker

If fluid level is correct and fluid is red in color and doesn't smell burnt, next up is to test your "throttle position sensor". The input from that sensor is critical to shifting characteristics of your AW4 transmission. Here is more.
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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.

jon with the jeep

awesome thnx now i have somewhere to start.. i was begining to think i needed a new trans but this is much cheeper if its the cause

jon with the jeep

i did have my fluid and filter changed when it first started and it got better for a month or so and now its back to its old ways

peep

Do continue with the fluid and filter changes. Cheap maintenance and not too tuff. There are a couple of hard pipe lines, a looped pair,at rear of the valve body, I have found them loose in past when servicing trans filter, push them up to insure they are entered tight. Ive got over 554000km on my AW4, fluid and filter every spring, still workin, ... jinx. Definately love that tjwalker test info, saved on favourites.

jon with the jeep

ok it took me awhile but i got around to changig my tps.. what a pain i figured out that i have a 97-01 throttle body on my 96 because the first 3 tps i got had the wrong size clips. so i changed it and it does run much much smoother, shifts nice ,idles perfectly. and it also stopped sticking for a day in what i thought was 4th gear but im pretty sure its overdrive now. but now it does it all over again. it just doesnt want to get out of overdrive unless i tap the breaks. i think this might be a torque converter issue. i think that controlls od from what ive read. so my new question is what would make my jeep stick in overdrive?? i have been loking around on here a lot and i think my next step is the transmission kickdown cable, torque converter lockup solenoid, and brake light switch prob in that order. what do you guys think am i going in the right direction? thank you in advance for any help

jon with the jeep

please help this is my dd and it does this EVERY time i drive now

mustangkraze

You may have a clogged valve in the transmission or a sticky spring

jon with the jeep

ok cool thats 2 more things i can take in to consideration i appreciate any input/suggestions at this point my jeep runs great besides this its my last problem i have to chase down thanks!

fathan16

it's not supposed to downshift when you take your foot off the peddle.... i have no experiance in transmissions but it almost sounds like one of the clutches is worn out.

has your transmission been overheating that you're aware of?

jon with the jeep

no i dont think its overheating or anything like that, this is really tthe only problem it has every other gear is fine. thats overdrive right when ur going between 40-45 mph and it sits in the last gear? i thought it was 4th but now im pretty sure its od.

Radi

If you drive at a steady speed, 45 mph or better then tap the brakes momentarily, the RPM's should kick up a couple hundred, that's the Torque Converter Clutch disengaging.
Does that work correctly?

Marks2000XJ

Gotta love these Jeeps. Mine just threw two codes last night. P0740- defective torque converter clutch or internal transmission failure and P0700- shorted or open circuit within transaxle or failure of transaxle control module. I heard this high pitched wining noise coming from about where the gear shifter is at about 30 minutes before it threw the codes.

Does it sound like my tranny is on it's way to the grave? Is there any way to save the tranny before it goes completely out, if that's what it is?

The guy at auto zone said if they fluid has never been changed don't do it now or it will definitely go out quicker. I bought some Lucas Transmission Conditioner to see if that would help for now.

Not sure what to do about this. Any help or advice would be great. The transmission seems to still shift out okay but that high pitched wining does not sound good for sure.

jon with the jeep

yes that works fine but thats the only way to down shift. if i coast from there without hitting the breaks to below 40 and try to speed back up it starts to buck and sputter. it always used to downshift on its own. i did the key trick for the obd and all i got was code 12 and 55 which means everything is fine so im kinda stumped again.

Marks2000XJ

I think my tranny is toast