jboyce6024

You could try resetting the adaptive memory in the ECM. I had a much similar problem in my TJ. Would run as long as you had your foot on the gas and would die as soon as you let off the gas. I stored mine over the winter and had some battery issues when I fired it up again a couple weeks ago. What I was left with was this start/stall problem. I did some research and found this procedure, followed it and so far so good. I also found the same procedure quoted in the factory service manual for the TJ. I wouldn't expect the XJ to be a whole lot different. Apparently this reset procedure brings everything back to factory settings and the ECM will learn your driving habits over the next 50 starts. Sounds like black computer magic but it has worked for me. See below...

Disconnect the POSITIVE battery Terminal and touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block will work as a ground. This is to discharge the PCM capacitors, which maintains the Adaptive Memory.

Reconnect the Battery Cable
Turn Ignition Switch to the “ON” position but DO NOT start the engine
Turn Headlights “ON”
Turn Headlights “OFF”
Turn Ignition Key “OFF”

Hope this helps.

trigger

i had something similar happen with my 99 WJ. really rough idle, stalled a couple of times but smoothed out somewhat once on the throttle. then it started getting worse. finally got an engine code, turned out it was my upstream O2 sensor. after replacing the sensor, looked like things were ok, and then it happened again. i drained the electrical system by disconnecting both cables from the battery and grounding them out for ten seconds. i reconnected the battery, fired it up and its been running like a top ever since.

try disconnecting the upstream O2 sensor, and start it up. if it doesn't stall after the usual point, this may well be your problem.

good luck, keep us posted.

oldfart

Crank position sensor problems are very common on Jeeps. They will NOT usually throw a code, which makes it difficult to diagnose, even if you have a scanner that reads live data. I don't like to suggest changing parts without hard evidence but it's the only thing I can think of that fits your issue. I assume you checked the fuel pressure and changed the fuel filter.

CTSHIRT

Everyone has said CPS from the get go and I believe they are correct. I ran more tests late last night and the jeep fired up.. seconds later it died. I tested for spark at the coil and there was non. Still no codes..

I assume the CPS sends a negative signal to the ECU and won't let me start it again after it dies. Since a bad CPS won't allow the ECU to send spark to the coil I can only assume the crank sensor (the most common failing part) is defective. My coil has a lot of dirt and rust on it so I will replace it anyway just to rule it out.

I have a CPS on order, I will post back letting everyone know the results after installing these new parts. Thanks again for all the help!

robic58

The one and only occasion my 89 Pioneeer died while I was driving was due to the Crank position Sensor.
It would die, restart, only to die again.

Obviously, can not assure yo that it's the problem, but worth checking out.

Good Luck.

oldfart

I'm surprised you had to order one, they are usually in stock everywhere.

CTSHIRT

It is alive! Thanks to everyone who replied and bestowed their cherokee knowledge! I swapped in a new crank sensor today and she fired up and idled great. I cautiously drove her around the block hoping she wouldn't stall and she didn't. I am still a skeptic but for now it's running, it's driving and it sounds great.

On a side note, I read a lot of reviews stating how difficult the CPS job was. I used 2 9" extensions, 2 6" extension, 2 u-joints and a 11mm deep socket (if i recall correctly). It was out in less time than it took to assemble all the extensions on my ratchet lol putting it back together i had a friend hold the new one in place while i put the screws in by hand from under the jeep and tightened with the ratchet.

Thank you again.

oldfart

Thanks for coming back with your solution and how you did it. It's not too bad to change on an xj but it's a pain in the butt on the zj or wj due to accessability. It can be made a little easier by unbolting the cross-member and lowering the transmission a few inches.

NathanM

Figured that's what it was, I have changed literally 30 or more of them, very common problem. Glad to hear it's working.

salad

Grats on the XJ! 1999 is a fantastic year! Hopefully yours isn't as rusty as mine.

I would continue looking at your electrical system for this issue. If your negative-to-fender cable was that bad, immediately ALL of the cables coming off of the battery are in question. First step is to disconnect all of them, clean them until shiny with something abrasive like a wire brush or sand paper, remove residues with a hexane electrical cleaner, apply an electrical corrosion preventative like NOALOX or OX-GARD (Home Depot has this stuff - and note these are conductive, NOT dielectric grease) and reassemble. If you notice any brittle or corroded cables they should be replaced. The copper conductors in stranded cables will continue to rust out up into the cable jacketing.

How is the engine dying? Are you losing it slowly at idle or does it just cut off? Slowly dying at idle points towards a charging system problem or IAC/TPS issue.

When you say you "cleaned the IAC" - did you push the pintle in or drop the unit? Have you tested the TPS?

Like a previous poster mentioned, CPS is a very common issue, but based on what you've already revealed (and how much they cost) other things should be addressed first.

In the 97+ XJs the fuel pump and pressure regulator are in the tank and the rail is always within 5 PSI of 49 PSI. If your fuel pump was failing you'd notice hard starting and probably a power limit if not enough fuel is delivered.