Zekedogg

Hi all new to the forum and have a question. I have a 99 XJ and the tranny wont always shift into 4th. If I pull over and shut it off and start out again it will usually but not always shift into 4th and sometimes it will shift into 4th then slip back down into 3rd. Any ideas?

Roler

Welcome to the forum.

What you can try is a few simple things to see if that improves your shifting.

Check the transmission fluid for level and quality first. If the fluid is dark, replace it. Shifting issues sometimes surpirsingly improve with nice clean fluid. You can do a forward flush and be done with it, or do several drain/refills to eventually replace all the ATF.

Check the throttle shift linkage (there is a 1 minute adjustment procedure for this, will see if I can find a link, but its mentioned in several threads, might have to do a search)

Check your throttle position sensor (TPS), This sensor is closely involved in shifting characteristics. Best to test with a non -digital (analogue) meter to check for any 'gaps'. If your TPS doesnt work properly, the shifting can be getting off. Search for TPS testing procedure.

See how you go with this and let us know. For future readers of the thread it is nice to see what worked and what didnt. And when you get back to us, we can help you further if things haven't solved the issue.

Zekedogg

I did change the tranny filter about a month ago but did not do a drain/refill to eventually clean up the fluid.
I will try these suggestions thank you for the reply.

tjwalker

Here is information about verifying the throttle position sensor and below that is a link that will show you how to adjust the TV cable, both good ideas from Roler!

Good luck and keep us posted!
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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.
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Here is the link to adjusting the TV cable.

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

DFlintstone

Well written Rooler. I'd be interested what codes it might have. Speed sensor or TPS? I just adjust my "kickdown" cable with almost "O" play using the button on the housing.

rzldzl

my 98 wouldnt go into 4th after driving an hour or so

code reader said OD solenoid was bad, replaced it for $60

fixed

Zekedogg

Thanks I'm getting the code read tonight, I'll post what the scanner says. Thank you for the detailed response.

Zekedogg

Had the scan done 3 codes popped up one for the TPS and 2 that say transmission circuit malfunction. Changed the TPS $51 at autozone with lifetime warranty, still had the problem then adjusted the throttle cable and lo and behold problem fixed.

I'm hoping that when I reset the computer that the TPS was causing the tranny codes.

Thanks guys.

DFlintstone

And the crowd Cheers! Well done! ........

(the "throttle cable" is attached to your foot, that other one goes to the tranny...."

Roler

Yay....