1994 Jeep Cherocar running issue

94xjsport94 · Jun 26, 2015

I'm working on my 1994 4.0 auto XJ. On a cold start it will start slow and run fine until everything gets nice and warm at operating temperature. Runs steady at 210 in park and neutral, haven't ever had it get hot on me in the last 2 years. Now as soon as everything is nice and warm it will start to stutter and run like ass until it stalls out and quits. It only does this in drive. Once everything is warm if it will restart- slow starting, not like a heat soak issue, it will idle fine in park/ neutral but as soon as it is shifted in to drive it dies. This issue started at Gulches in October but has gotten much worse. It started shutting off when it got warm but I could just turn it off, let the e fan run for 10-15 min, and it would fire right up and go. Now I had to get towed back from the bottom of Boatramp and TNT... I rebuilt the engine last summer and drove it to work for 2 months before I did my 1 ton swap. I have replaced the fuel pump, filter, pick up screen, ignition coil, and checked for CEL codes. No codes at all and the light does work. It's very similar to an issue I had about 4 years ago when I had a broken wire in the 5V return to the ECU from the TPS, except that gave a CEL. I will replacing the CPS and battery tomorrow with some good spares I have. I feel like it is a sensor that is getting hot and breaking down. Aside from that, I am at a total loss with this thing. Please help!

zjtrey · Jun 30, 2015

I think the crank position sensor is probably the culprit here, it could be as simple as its a little loose and not always close enough to the reluctor ring on the flywheel to tell it when to fire..

another place to look is the sensor in the distributor, I think it acts as the cam position sensor if i remember correctly.

Also check the wires going to the upstream O2 sensor, its easy to route those wires incorrectly and they'll hang on the exhaust manifold and eventually short out causing a no start.. when i replaced the motor i routed the wires incorrectly and it was nightmare to figure out.. taped the wires back up, zip tie them out of the way and never had another issue

94xjsport94 · Jun 30, 2015

That's what I've come to the conclusion here. When it dies it is drops the ASD which also drops the fuel pump, most likely cause is the CPS. The cam sensor is in the distributor. I also had an issue with that O2 sensor wiring about 4 years ago but I fixed that like you said and it looked ok now. It's at a shop getting looked at so I can hopefully go to harlan this weekend... The thing that was throwing me off was the fact it died while going in to drive but would idle fine in park/ neutral.

zjtrey · Jul 1, 2015

the crank sensors can be finicky bitches… make sure they put a quality one on it from napa or oreilly, i've had advance auto ones be bad out of the box and really throw you off..

kinda sounds like it might be just loose, extra vibes from driving causing problems, but they can wear out too and not oscillate correctly in the housing also.

those are the only two sensors that will stop a 4.0 from running… the other one that will cause problems is the MAP sensor, if theres a problem with it, the motor won't rev above 3500 or so and is usually associated with a vacuum leak.

The 4.0s are great motors for what they are, i've had ton of fun with them. hope you get it going

94xjsport94 · Jul 1, 2015

Had a broken wire in the ASD relay circuit, fixed. Broken wire in the injector power harness, fixed. That had a funky little apparatus on it where it broke.

Wheels off the ground the Jeep will run in drive but as soon as you apply the brakes it dies... Unplugged the solenoid harness and it does the same think. There is either some ****ery going on with a shared ground somewhere that can't handle the brake lights interlock with the unlocking convertor switch or the locking convertor solenoid is stuck in the wrong state and when it's warm and heats up, it kills the engine.

ranger11 · Jul 1, 2015

Re:

Disconnect the brake light switch.

Neal3000 · Jul 1, 2015

Heep 4.0 is your problem

94xjsport94 · Jul 1, 2015

It appears as if the injector harness was the source of this fiasco. Now the radiator is blown up in it... Must have broken down over time and gotten worse the more it ran/ went wheeling.

mdo817 · Jul 1, 2015

Re:

I have a harness but my spare radiator is in Ranger11 ' s race Jeep

94xjsport94 · Jul 1, 2015

I'm buying a new radiator first thing tomorrow.

mdo817 · Jul 1, 2015

Re:

I will be meeting Jduck at Summit tomorrow evening or you could come down here anytime tomorrow if you need the harness, long drive, but it's a good price

94xjsport94 · Jul 1, 2015

I bought a 95 on Saturday to rob parts from and part out actually. I've got to pick it up and fix it tomorrow before work then load everything up and drive to harlan when I get off. It's going to be a long two days. The injector harness should be fixed and eliminate this issue but I can't test anything else until the radiator is fixed.

Neal3000 · Jul 2, 2015

How many parts heeps does it take to keep one good one alive?

94xjsport94 · Jul 2, 2015

mdo817 · Jul 2, 2015

I am down to NO parts Heeps Neal, kind of spookie really, but I do have several big bins in the shop full of extra parts. LOL

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