95 Sport. Automatic.

Today I was driving to work and once I hit about 65 the transmission kept jumping between 3rd and 4th gear. After a bit of this I slowed down once I hit traffic and the trans dropped to second gear. I got off on the next ramp and it shifted back up to third just fine but still jumped between 3rd and 4th.

This was running and shifting fine on Wednesday, didn't drive it Thursday and the issue appeared today (Friday). The only maintenance I have done between Wednesday and today was a tune up. However, when I put in the new throttle body I never adjusted the kickdown cable since it was shifting fine without an adjustment. Would an improperly adjusted kickdown cable cause the trans to keep shifting between 3rd and 4th at 2500rpm? I hit 2500rpm in third, the jeep shifts to 4th and the rpms drop to 2000 then it shifts back to third until 2500rpm rinse and repeat. (I know I know, get out there and try it. However I am at work right now so I'm gathering up ideas to try later today. )

The fluid is dirty and I'll do a drain and fill before I leave work but I won't be able to do a filter until later. I'm hoping it is something as simple as dirty fluid.

I'm really hoping the trans isn't taking a crap on me. Before this happened it shifted smooth and good.

On a side note, does anyone know the wrench size of the drain plug on trans? All my tools are at home so I'll have to pick one up or have one dropped off.

Thanks

 

Dex II or ATF-4 for replacement fluid?

 

1. Use Dex/Merc III compatible fluid. Not ATF+4. If fluid is really dirty, perform a "drain and fill", then drive for a week and repeat until the fluid stays RED in color and does not smell BURNT. Be careful not to overfill.

2. Adjust your TV cable. Only takes 5 minutes.
https://www.cherokeeforum.com/f2/free-quick-fix-41821/

3. If fresh fluid and a TV cable adjustment doesn't help, the throttle position sensor might be suspect. Here is more on that important engine management sensor.

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.

 

I just did the tv cable and I'm going to add some new fluid. I'm at work though until 1am so I won't be able to test it out until then.

Hopefully it isn't the tps. I just put a new one in a few weeks ago but non-oem ones are prone to failure so eh..could be.

 

Made it home without issue but it still shift hards from 1-2 and 2-3. Going from reverse to drive and vice versa makes the jeep jump pretty good too. That could just be worn mounts though I think.

Going to do filter today and get a good look at the fluid.

 

Filter is not immediately necessary to replace. Like TJ mentioned, drain and fill till fluid remains red and you should be ok regarding this.
(Dropping the transmission pan is not exactly the "remove bolts-drop pan" like Haynes mentioned and the filter is a screen really, and you could do it on your last drain-refill if you still feel its needed)

 

I did a drain/fill today and put in 2 different TPS (one oem and one not oem) and the thing still can't figure out what gear it wants to be in. As soon as I hit 3rd gear it'll go in to 4th shortly after then drop back down to 3rd and fluctuate between 3rd and 4th unless I keep the gas pedal fully depressed then it stays in 4th but that results in me going faster than I'd like to in this beast. Lol

It shifts from 3rd to 4th around 2500rpms then the rpms will drop to around 2000-2250 once it is in 4th. Then it'll downshift to 3rd almost instantly until the rpms hit 2500 again then back to 4th and right back down to third. It just repeats it endlessly. Hopefully that clarifies it a bit better.

None of this started happening until I did my tune up (plugs, cap and rotor) but, as far as I know, none of that crap has anything to do with the transmission shifting improperly. It was perfect until the tune up so either I messed something up or it is just an unlucky coincidence.

 

I made a video so as soon as it is uploaded I'll post it here so yall can see what I'm talking about a bit better.

 

http://www.youtube.com/watch?v=72yCv...ature=youtu.be

Watch the full 2 minutes and you'll see it happening while driving and while accelerating from a dead stop.

Make sure to increase the resolution to at least 720p or it looks like crap.

Oh and my phone didn't record audio.

 

Can a vacuum leak maybe cause the transmission to act like this?

I'm really lost.

 

A couple of things to check:
1) TPS voltage @ the connector. Make sure it tracks throttle movement in a linear manner with no flat spots or dropouts. (key on, engine off, probe center connector to ground. Slowly open throttle by hand, voltage should increase smoothly.)
2) Wiring and connectors to the TPS, TCU, Transmission solenoids and speed sensor. Take the connectors apart and clean the pins and sockets.
3) Grounds. Particularly those two bolts near the coil where the trans grounds.
4) Verify the cable adjustment again. Might try setting it a click tighter or looser to see if that changes anything.

 

Tps is good. I'm not sure where the TCU or the trans solenoids are so I'll have to consult the manual for those locations.

Thanks for the suggestions and I'll update tomorrow!

 

I'd check the TPS anyway by measuring the voltage across the full throttle range from closed to wide open, it's very important in determining shift points. If you have a dead spot the trans is going to hunt. The TCU only has it and the speed sensor to go by.

The TCU is normally just below the glovebox, passenger side. There should be an inline fuse and a resistor pack in the harness.
Trans solenoids are in the transmission, the harness comes up to plug over near the trans. dipstick. Check all the plugs over there, they are subject to heat, oil and vibration. Don't forget the two ground studs on that side of the motor too, located near the coil.

 

I'll double check the tps again just to be sure and I'll go over everything else you and cruiser have told me. Appreciate the assistance and hopefully I can post up some positive results tomorrow.

 

Fixed for now. Cleaned all the connectors with contact cleaner and found a ground that came loose on the front of the block.

I took it for a test drive up to 70 a few times but I'll know tomorrow for sure after extended highway travel.

Thanks gents.