Hello! I'm new to posting here, but I've been lurking through the forums for a few years.

I have a 2000 Cherokee Sport that was, until a couple weeks ago, my very reliable daily driver. It's a 4.0L l6 with an auto and a 231 transfer case. The chassis has about 240k miles and I was told that the engine has about 100k less than the chassis according to the previous owner. I believe that it has an earlier engine due to the lack of bolt holes for the coil pack mounts on the head.

A few weeks ago I was driving and went to accelerate after waiting for a light and it felt like the engine cut out momentarily. I put the skinny pedal down and it picked up and all was fine for the rest of the day. The next day it did it a couple more times, but it turned from a hiccup into a lurching where it feels like it was cutting in and out over and over. Then it would clean up for a bit and do it again. Watching my tach it jumps between 1500 and 2000 rpm, up and down, up and down. Since this was my daily driver, I continued to drive it while working on it every night. After a week or so, it had gotten so bad that I had to stop driving it. It currently goes won't drive down the road at all without cutting out constantly. It doesn't matter if the engine is cold or hot. It starts immediately when I hit start down the road. I have no set or pending codes. I tried the key trick - turning on the key while holding the odometer reset button. The odometer counts up then shows the mileage. No codes flash. No 12 or 55 even though the battery has been disconnected due to some of the work I've done to troubleshoot it.

The engine idles fine and revs perfectly in neutral. I can't get it to repeat the problem unless it's moving. It starts up immediately and never completely dies. When the rpms drop, it picks right back up.

Possibly relevant repairs:
- The previous owner stated that he did a "coil pack conversion: when he swapped the engine. The ignition appears to be stock for a 2000. The engine appears to be out of an earlier jeep due to lack of coil pack mounts on the head, but I don't know what year
- The crank position sensor was changed by a shop about 2 years ago after it died on the side of the road. The clip had come off the firewall and the connector had melted to the manifold. I'm not sure what brand they used, but I was stranded so I had the shop fix it.
- A year ago, I replaced the injectors with 4 hole injectors (neon?) since the original ones had rusted and cracked the plastic housing off. They were brand new and came with the jeep as spares.
- A couple months ago, it was raining pretty hard and the horn came on in the middle of the night. It was 3 AM and the horn wouldn't turn off so I pulled the relay. When I reinstalled it, I couldn't repeat the issue so I took the relay back out in case it happens again. If I install the relay, the horn works as designed.
- I have (had?) a pretty severe oil leak. It appeared to be leaking from the valve cover gasket, so I replaced it about a week before the issues started. I'm not sure if that completely fixed the leak or not since I can't drive it.

What I've tried:
- Tested TPS. It checked out fine, but I replaced it anyway. No change.
- I cleaned the throttle body. It looked relatively clean to start. I didn't have enough carb cleaner so I didn't clean the IAC or MAP. I have to go back in for those.
- Unhooked the clock spring due to the horn issues and reading that the horn and TPS may share a common ground. No change other than the airbag light coming on. Reinstalled. Airbag light went off.
- Unhooked the upstream O2 sensors. No change (other than CEL for o2 sensor) so I hooked them back up. CEL went off.
- I checked the fuel pressure and had 45 psi at the rail. I changed the fuel pump, screens, and FPR/filter gizmo. The pickup screens looked pretty dirty, I now have` a constant 49 psi, but no change in how it runs.
- I changed and regapped the spark plugs. No Change.
- New coil. No change.
- I checked (visually) for broken vacuum lines. I found one questionable vacuum line connection hose and replaced it. No difference. The rubber vacuum elbow on the MAP sensor looks good.

What I'm planning on looking at (in no particular order)
- Clean all grounds
- Crank position sensor (test/replace)
- Cam position sensor (test/replace)
- Alternator (junkyard alternator swap? maybe new?) - someone on the forum said a failing alternator could cause cutting out?
- MAP sensor (replace)
- IAC (clean and/or replace)
- Buy a cigar and smoke test for vac leaks
- Check torque converter bolts - maybe it's locking/unlocking and it just feels like its cutting out?

My gut feeling is that it's something electronic, but I don't know where else to look beyond the list above. I'm starting with the grounds after work tonight. I'm assuming it's something simple, but I'm quickly running out of things to poke at.

What am I missing in my list? Is there an order I should tackle this? I'm not sure how to test some of these things. I have no issues with replacing parts if it means my vehicle will be more reliable since I have no idea when a lot of this stuff was done last... but I don't want to throw money at it just for the sake of throwing money at it. I'm also worried that I may be introducing more variables even though I've been going with genuine mopar parts.

I'm currently driving my [barely] street legal track car to work every day, and camping season is almost here. I'm almost ready to go nuclear and just buy an entire drivetrain and wiring harness at the junkyard. I'm at a loss and I could really use some help.

Thank you!

 

So I found that a couple of my fuel injector wires had cracked insulation. On a hunch, I pulled a nicer wiring harness out of the junkyard and swapped it in. It doesn't appear to have helped at all other than cosmetically looking better.
I also cleaned all of the grounds in the engine bay and replaced the map sensor with no luck, so I can check those off the list.
I purchased a bluetooth OBD2 reader (BAFX) so I can now see what all of the sensors are doing in real time. Although, I'm not really sure what to look for. I haven't had much time to play with that yet other than to verify that the issue happens both when running in open and closed loop.

I'm very confused that I still don't have a check engine engine light. I'm beginning to wonder if my pcm is going bad although I understand that that would be pretty uncommon. It also doesn't explain why I only have issues under load. I would think a bad pcm would cause a no start or at least manifest itself regardless of the load on the engine. Regardless, I bought a pcm at the junkyard for $12 because it was the only one there.

I haven't had a ton of time to wrench since the timing belt snapped on the car I've been driving and I need to fix that to get to work. I'm planning on spending Saturday wrenching on the jeep.

I could really use some help here. I'm pretty capable when it comes to the actual wrenching, but troubleshooting isn't really my strong suit and I know throwing parts at it is the wrong approach. Please help. Anyone?

 

Add checking the bellhousing to engine bolts are tight to your to do list.

 

lawsoncl, I owe you a nice frothy beverage of your choosing. I got under there this morning and checked my bolts. The passenger side bolt tightened by about 1/8 turn. The driver's side bolt was completely backed out, the driver's side e12 bolt was missing. I verified that the other e12 was there, but I'm not sure if it's tight. I suspect it's not. There was a visible gap between the bellhousing and block.

I need to go to the parts store and get bolts to replace the E12s. Are they just 3/8-16x1 7/8 bolts? I found a diagram on here that shows that being the size for 88-96 XJs. I just wanted to confirm that it's the same for later cherokees.

It's odd that they were loose because it's been probably 5 years since the engine was changed out and it's been daily driven since then. But it appears that was my problem... Or at least one of them. I'll probably use some blue loctite so they don't back out again.

Thank you so much!

 

Loose bellhousing bolts seems to be cropping up more and more on these 20+ year old vehicles. When that happens, it acts like bad crank sensor as the flexplate moves out of alignment with the sensor. If you still have issues after getting it bolted up tight, you might want to pull the crank sensor out and see if the end got damaged by the flexplate.

They don't need to have the E12 head, and yes it's the same bolts for all the years. Lots of folks just replace them with hex bolts with the integral washer (sometimes called hex-washer, flange head or hex-collar bolts). If you go with a regular hex head and a separate washer it'll need to be a fairly small diameter washer to sit right in the slot. A regular hex head might not give you enough room to get a thick wall socket on it.

 

GENIUS I say..just pure Jeep Mechanic GENIUS..

 

Nah, just seen this first hand a few times and a few other posters here and on NAXJA have run into this.

 

Just to put this thread to rest, after chasing my tail for weeks, tightening the bellhousing bolts has completely solved my issue. Even with a 1" TC drop, the bolts at the top of the bellhousing were a bear to get to. Ifor anyone who finds this thread in the future, I ended up using two 24" extensions and a swivel joint to get my torque wrench behind the transfer case. Total repair cost: $1.20 for one new bolt. Now that the problem is solved, I plan on pulling all the bolts back out and putting a bit of blue loctite on them... But that can wait for a nicer weather when I change out the trans mount. Dropping the transfer case another inch or so should make the process a lot easier. For now, I'm just happy to have my old girl back. Thank you again lawsoncl!

 

I had a similar issue, but only did it until it got to normal temperature. I fixed it by changing the injectors.