Technik

XJ is a '98 4.0L Sport, 4x4, automatic.

I have recently done:
Champion plugs
Wires
Cap
Rotor
TPS replaced ~3 days ago
Battery cables and clamps
Known good ASD/Fuel pump relays

The truck was intermittently stumbling on the highway (maybe once every 10-20 miles of driving), feeling almost like I had hit a pothole. Loss of power for a split second, then back to normal.

I replaced the TPS a few days ago as it looked to be the original part, and for the past three days the truck has run flawlessly. Felt like it had more power, no more stumbles or "cut-outs", trans shifting much smoother, etc.

Today I went to lunch at work and the truck shut off completely whilst going down a curvy road. I threw it in neutral while rolling and tried to start it back up, but no luck. Pulled off to the side, sat for a second, turned the key and it fired right back up. No CEL, no codes stored. Readiness monitors on the PCM are still showing OK, not incomplete, so I don't believe the PCM is resetting.

CPS checks out with an ohmmeter (infinite resistance between pins B & C, 5V on supply wire), but I haven't gotten it to fail consistently enough and predictably enough to test the sensor when it won't crank. The truck has had a hard starting issue related to the check valve in the fuel pump assembly for some time (at least a year and a half) but pressure has always been dead on 49psi while running and it hasn't made any noises or shown any signs of an issue.

I did notice when cycling the key that I didn't hear the fuel pump priming like normal. Could have been road noise but I can usually hear it every time if I listen for it. Would this point to the CPS? I am also going to zip tie the PCM connections for the drive home (~20 miles) and see if anything improves.

Muaddib420

Refreshed your grounds?

Technik

Scrubbed/wire brushed all ground points to bare metal when I replaced the cables, including the braided strap to the firewall.

Roblaza

Sorry to jack, but I'm having a very very simar issue with my 99. It's been ittermittent for the past 3 months and its extremely frustrating. Almost identical to what you're describing..it'll run great until up to operating temp then it'll randomly sputter like its starving for fuel and it'll die; faster if I hit the gas. It'll start up again right away but will run rough and die until its cooled down.

I've done:
CTS
CPS
TPS
fuel pump
Injectors (784 neon injectors- new)
Plugs
Wires
Rotor
Cap
aswell as refreshing all grounds.

No CEL, but I have yet to get it scanned for stored codes. I haven't found a solution yet, but I was thinking it could be coil related.

I'll be watching this thread intently to see if a solution is found and to update with any progress I make as it may help you too.

Gee oh Dee

Check your coil, esp if it does when hot but runs when cold.

If that doesn't pan out, check fuel pressure when hot.

Technik

No hot/cold correlation. Just as likely to do it 30 seconds after a cold start as it is at full operating temp. Will check primary/secondary on the coil.

freegdr

Sounds like fuel issue sensor issue would throw a code .

Technik

I'd be inclined to agree but it cuts out sharply... my experience with fuel issues have always caused a "sputter." This is sharp, like I switched the key off for a split second.

Gee oh Dee

Only one way to be sure...

emptypockets

Does it happen only under a load? Only on turns? Fuel levels in the same area when it dies? I'd check fuel pressure and find someone with a scanner (who knows what they're looking at) to do a drive along and monitor the data, or set it up to record your data.

freegdr

Exactly ....Or throw all kinds a money in sensors on it like a lot of others do then were right back here.

Technik

No correlation. Has occurred so far on a full tank and nearly empty tank and everywhere in between. Have tried different stations and brands of fuel. Happens on acceleration, at idle, and cruising at highway speed. I have tried to "**** it off" going down bumpy roads, bucking the throttle, tapping it sharply, etc. but I can't induce this problem -- it just occurs seemingly on its own without any sort of particular action to cause it.

The only interesting set of circumstances was that it literally hadn't done anything at all for the past three days after I replaced the TPS. Ran like a new Jeep until it shut off today.

Technik

Just got done replacing the crank position sensor. The split loom and wiring harness insulation had all melted together to the point where I believe the wires were shorting together. The truck is running smoothly right now, with no misfires or hesitation. I guess we'll see what happens. Borrowing a fuel pressure tester from a friend later this evening.

Technik

Pressure tested to 49psi while running. Still no misses or cutouts after changing the crank sensor. Checked tightness of ground connections and zip tied the connectors to the PCM.

Hoping this is fixed, I hate chasing gremlins.

Gee oh Dee

Mine were toasted like that and showed the same symptoms.

Its better to confirm before throwing money at the problem.