Alright, so… Last night, I gave my Cherokee a little tune up (plugs, air filter, oil change), and afterwards it started strong and ran fine. I took it to work this morning (11 miles), no issues starting or driving. I take two breaks when at work where I drive off property and had no problems. I left for the day and drove about 10 miles. Sitting at a red light, the jeep starts to idle low, and then it stalls (within 5 seconds of idling low). It won’t start now. It cranks strong but never starts. I still have power to radio, lights, windows, etc. No codes or lights thrown.

I replaced the crankshaft position sensor about a year ago. It wasn't too bad to do, just was hoping it wasn't that again. I won’t be able to get to it until at least tomorrow evening, but my thoughts were to start with fuses and relays, then confirm the fuel pump is getting gas to the engine, throttle position sensor, and camshaft position sensor. If anyone has any other suggestions, please share. I've read numerous forums about similar problems, but every time you think you’re about to see the post that confirms what everyone has been guessing, the OP never posts the follow-up (of which I have been guilty, but never again...because that just sucks).

Before the tune up, it had an occasional misfire in cylinder 6, and you could just feel the hesitation to start. It would start, but you could just tell the plugs were in horrible shape… and they were. Other than that, I had no problems. Any input is appreciated.

 

I think your plan is good, that sort of drop-off sounds like a fuel delivery failure to me.

 

Have you checked for a spark on all cylinders?
Have you unplugged the Crank Position Sensor for a few seconds?
Have you confirmed that the Cam Position Sensor is good?
Have you cleaned all chassis and engine grounds?
Have you done a thorough cleaning of your throttle body?
Have you plugged in a scanner and checked for codes (regardless of the CEL status)?

 

I agree with sounding like a fuel problem. Your 01 should have 49psi at the fuel rail. I would start by checking it for codes fuel pressure and for good measure you may want to make sure that you have a strong blue spark. But it really doesn't sound like a spark issue. Let us know what you find.

 

last night, about 6 hours after the vehicle stalled and wouldn't start, a buddy gave me a ride down the road and we we're going to tow it back to my place. Decided to give it a shot first and it fired right up. This morning, i drove it to work with no problems. Left for break and on my way back it stalled while coasting around 20mph and would not start again. Sprayed some throttle body cleaner straight into throttle body and was expecting it to ignite but it did nothing. Jeep just kept cranking. Had to leave it in a parking lot and had a coworker pick me up. I'll be heading back to it in an hour or two to check if it'll start. I'll let you know. Still no DTC / codes or lights being thrown.

 

alright...went back to it after it sat for about two hours... fired right up and drove it straight home. I was thinking a sensor originally but after the throttle body cleaner didn't ignite when cranking I'm wondering now why there was no spark. I assumed from past experience with other vehicles that it would have fired up when spraying directly into throttle body. ??? Can the coil rail fail intermittently when it starts heading out?

 

Yes they can. Mine on my 98 did it, that's why I say Yes.
If you aren't getting spark, it can possibly be the coil or the cps. I know that you said that you changed the cps. But if you replaced it with an after market one they tend to have a very short life span, If they work at all.

 

Replaced with an Advance Auto replacement.

 

the difference in symptoms between my current situation and the time i replaced the crankshaft position sensor, is that last time, it occasionally wouldn't start until it finally gave out and wouldn't start at all. I didn't experience the stalling while driving last time.

 

I'm not going to say with certainty that's your problem....but it might be. The XJ's aftermarket electronics have a really bad track record, and this is the cheap end of aftermarket.
Dealer part, if that isn't possible NAPA has a reasonable alternative.

 

Talked it over with the "Master Technician" at the Jeep dealership and ordered crankshaft sensor. Won't get to me until tuesday. I'll post what happens.

 

just attempted to swap crankshaft sensor, and couldn't remove bolts. They're not even rusted. so, going to pick up air impact wrench this week and try again. Would've kept trying but kept slipping and rounding the bolt. Quit before it got too bad. Don't remember putting them on that tight before. I'll post when finally done.

 

ok... sorry for the delay, but decided to give vehicle 1.5 weeks to make sure my problem was truly fixed. Replaced the crank sensor and everything has been good. When holding the parts, you could see/feel the difference in quality between the OEM sensor from Jeep, and the sensor from Advance auto (darn aftermarket parts). Thanks for the help and suggestions.

 

Good to hear that it was the Crank-Sensor. Just to confirm, you originally replaced it with a CS from Advanced Auto Parts, and now this time you grabbed one from the Jeep dealership? I'm having similar symptoms and have replaced a few things so far (fuel-filter, camshaft position sensor, coil-rail) and now am leaning towards the Crank-Sensor. Thanks!