Yea, I've tried - unfortunately it doesn't change anything. Pumping the pedal just causes erratic behavior while the RPM's and spiking up and down

 

2 - Fuel pressure testing tool - Available at local parts store as a loaner tool (https://www.autozone.com/loan-a-tool...it/913437_0_0)
3 - Compression Testing tool - Also available at local pars store as a loaner tool (https://www.autozone.com/loan-a-tool...et/424906_0_0)

You leave a deposit (covering the cost of the tool in case you never return it) and get your money back upon return of the tool.

The youtube videos will show you how and where to hook them up and how to run the test.

 

It took me a little time but I finally got it done. It was my first time testing fuel pressure and compression so that was fun.

1. Solenoid's tested at the TCM produced the correct resistance/ohms - I do not suspect a shift solenoid issue now.
2. Fuel Pressure test was pretty straightforward and the result was 45 PSI, which is within manufactured specification
3. Compression test results are below, looks normal

test 1 test 2
174 175
180 185
175 176
180 181
185 186
186 187

I am really glad I ran these tests instead of throwing parts at it, saved me from purchasing solenoids I didn't need...

But now I am at a loss for what to troubleshoot next.
The only sensors I haven't replaced are the o2 sensors, could that be related?
If Fuel, Compression, and Solenoids are the issue, do I have to start learning about AW4 Transmissions?

 

Boy this is a strange one. My gut feel is that it is engine management related rather than transmission. Next thing up if it were in my driveway would be to test the "throttle position sensor". Below is more on this sensor.

If you get stuck on this, you may want to take this to a trusted shop where they can put a scan tool and other testing equipment on your XJ and look at live data to figure out what might be going on. I commend you in that you are digging into this problem, but also realize that a shop can often pinpoint the root cause faster and more accurately than you can, especially if it is something repeatable and this appears to be repeatable. Sometimes the best money you can spend is on an accurate diagnosis by a qualified technician.

Good luck and keep us updated on this one!
-----------------------------------------------------------------------------
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 started with the TPS, I basically replaced it with a brand new Mopar one and nothing changed. I will try and test the resistance as I have a multi-meter but I gotta believe the mopar one I ordered off amazon is not going to be faulty.. at this point would be great if that was the issue :-) will test tomorrow and report back. The way I see it, I'm still improving my diagnostic skills

 

Sorry, missed that replacement of your TPS on your initial post. Yes, you are improving your diagnostic skills to be sure.

1. I didn't see mention of freshening all engine grounds, or did I miss that too....critical to proper engine management.

2. I'd sure like to get a scan tool on this. A 99 OBDII would provide quite a bit of valuable data.

3. It would be interesting to see if fuel pressure "fluctuates" when you have these symptoms. Testing fuel pressure at idle if it is not symptomatic may not tell the whole story.

4. The MAP sensor should also be tested. Be sure that the vacuum line leading to that sensor is pulling good vacuum.

 

Awesome thank you!!

1. I haven't done this but will start looking into it.
2. I have an OBDII reader but honestly the read-outs are a little over my head. I know how to check a CEL with it, but besides that the data captured and displayed doesn't really make sense to me yet. What should I be looking at here?
3. I was wondering about this as well. It only happens in motion and in drive. Is there a way to test fuel pressure related issues while driving? It seems to be that RPM jumping could absolutely be related to fuel not really being delivered correctly/right quantity for the mixture.
4. roger that, will get the multimeter on it

 

it does not look like a transmission issue. looks tps or ignition related. id double check the tps and ign components along with all ground wires and go from there.

 

Alright, so today I installed the Distributor Pickup Coil (Mopar), sometimes called a Camshaft position sensor. I've been driving around all day and it feels like a huge amount of improvement. I drove to auto part store and picked up some hose clamps I needed. On my way home the issue hit me again. RPM's started bucking and at stop sign the idle dropped super low. It only happened one time, then I heard a loud pop and it corrected itself / went back to normal. The computer reset when I installed the Distributor Pickup Coil so maybe this is just related to calibration.. I am hoping that is all it is and that the issue is fixed.

I'm going to drive for the next 2-3 days regularly and if the issue is persistent I'll assume it is something else. If it goes away then I'll move on to the next task! Stay tuned

 

Right.. well.. Kurt (name of my Cherokee) died on me in the middle of the road after some SERIOUS bucking and RPM jumping. I am convinced that replacing my Distributor Pickup coil is not the issue. Welp, at least there's a new one in there now!

Surprisingly for the VERY first time since this issue began, he threw a CEL when it stalled.. and I got a code!! Jeeeeez never thought I'd be happy to see a check engine light - the code is
P0132 - O2 Sensor Circuit High Voltage Bank 1 Sensor 1

I have both downstream and upstream Mopar O2 sensors ready to go.. I tried to replace them once but couldnt get the downstream one off.. so I just ordered a blow torch for that SOB. I cant imagine a faulty O2 sensor causing this sort of behavior but I suppose oxygen + fuel being incorrectly mixed/regulated is a pretty important thing..

When the torch gets here.. I'll report back in after swapping the o2 sensors out.

ps.. going to just continue updating this thread even if I'm talking to myself

 

"....talking to myself"

Nah, just a quiet, breathless audience full of anticipation!

 

Just reporting back in.. that replacing the O2 sensor (Upstream).. FIXED THE ISSUE!!!!

Man it feels good to have finally figured out what the problem was!

Things I tried that did not work
1.) New Mopar TPS
2.) New Mopar CPS
3.) New IAC
4.) Clean Throttle Body
5.) Adjust Kickdown Cable
6.) Test Fuel Pressure and Compression (all good)
7.) Replace spark plugs, wires, distributor cap and rotor
8.) Replace Distributor Pickup Coil (which is not not a camshaft position sensor)
9.) test the shift solendoids with a multimeter at the tcu
10.) Danced around and prayed to the Cherokee of past years for help

Woot woot

FIXED:
Replacing the Oxygen Sensor (Upstream) resolved my RPM jumping bucking issue (hesitation?) and ALSO fixed my low idle at stop signs which sometimes would die and other times just fix itself randomly.

This was fun (and stressful) but I learned an incredible amount about what it means to be a mechanic and how to troubleshoot stuff. Plus I now understand how combustion engines work. #worthit

Thanks everyone who input on this thread.. Onward!!