chipmaker

Needing a little help guys. A couple of days ago my trans. started acting stupid. When I fist crank up the rig in the morning,the first shift from first to second gear shifts flawless. The second time I start off it will not shift into second untill I let off the throttle at around 3k RPM and allow the trans time to shift. After that it "soft shifts" into second untill I stop, put it in park, turn the engine off and re-start. After re-starting it shifts perfect. Also some times it won't shift into or will not stay in over drive, and again stopping and re-starting the engine will remedy the problem. From what I have read it could be the shift solenoids or the TCM. I havent had time to have a code scan yet so I'm not sure what codes I have. Just wondering if you guys have any ideas or suggestions as to what it could be

RTorrez1

How is the fluid level? Also how does the fluid look, Is it bright red like it should be or is it a brownish color? Also does it smell burnt?

tjwalker

Don't forget about the "throttle position sensor", input from this sensor directly affects shift performance. Here's 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 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.

chipmaker

Thanks for the quick replies.

The fluid dosent look the best. Its a light brown/red color but it still smells like trany fluid and not like burned fluid.

Gonna pick up an analog multi-meter tomorrow and test the TPS if this monsoon we're having lately ever stops.

HudsonN

Adjust the Kickdown/TV cable as well. Makes a world of difference and even if that's not your problem it sure as hell will help.

tjwalker

Here is a link on how to adjust the TV cable. Only takes a few minutes. Your problem sounds electrical (if it changes when vehicle is turned off and restarted) but don't rule anything out.

https://www.cherokeeforum.com/f2/free-quick-fix-41821/

Radi

If re-starting the engine fixes it, take a good look at the TPS. Agreed with adjusting the TV cable, it has a direct effect on trans line pressure.

rlssteiner

My money is on shift soleniodes I had a similar problem with my old jeep a while back the transmission was actually bad.. Got a replacement and the soleniodes in new one were bad haha.. The cheapest I found brand new were 150 for all 3

salad

1. Replace that fluid. Red or pink depending on brand is correct color. Burnt fluid affects performance and longevity (cheap, needs to be done. Don't need to drop the pan. If you do, the 'filter' is a screen and can be cleaned with brake cleaner)

2. Tighten up the TV cable as suggested. Free

3. Test your TPS as per tjwalker's instructions. Free

chipmaker

Just an update. Been crazy busy at work lately and heven't had much time for the jeep.
Ok so, I changed the fluid, and adjusted the TV cable and still had the problem. While at the parts house looking for an analog multimeter to check the TPS I borrowed their code scanner and found that it had codes:
1682 low voltage from alt.
P0700 trans. control system malfunction
P0753 shift solenoid circuit
P0715 input shaft speed sensor circuit

After clearing my codes the Jeep has been shifting perfect since last Friday


Could it just have been a code in one of the computers that was causing all the fuss?

cruiser54

Could be resistance in the trans plugs over near the trans dipstick tube. Look something like the ones in the photo below. This photo is of a 1990, but you get the idea.

Cruiser’s Trans Plug Refreshing

Over near the transmission dipstick tube are 2 rather large connectors. One is black and the other gray. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.
Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.
　

ckysodkorn_xj

yes a stored code in the tcm can cause a trans to do funny thinks like stay in limp, but you're was not. keep an eye out for it to come back, and check to make sure you have reverse lights, if not rebuilding the nss is in your near future. and its easy.

chipmaker

Well my luck ran out.... tranny started acting stupid and re-starting it and resetting the codes dosent help. Still getting the P0715 and p0753. Since it's my daily ride and it will be this weekend before I can really start testing, I disconnected my TCU and plan on shifting it manualy for a few days. Dose anyone know if doing this will damage my trans?

Also someone told me it could be one of the speed sensors on the side of the transmission. What y'all think?

DFlintstone

Until someone smarter comes along, I think you can shift it manually. I'd be after that TPS first....Idk about the codes or speed sensor. The TPS actually has moving parts that wear.

chipmaker

Cool deal. I didnt think it could be any worse on it than the way it shifts at random with the TCU connected. After the code clearing seemed to fix it I didnt worry too much about testing TPS. Found out we have an old Simpson analog meter at work , gonna test it tomorrow on lunch.

Thanks for the help