djlarroc

1997 XJ 4.0 193k Auto

My jeep has died the last 2 times it has been offroad. Otherwise, it has been running fine.

The first time (3 weeks ago), I was going up a small hill, and stopped to wait for a friend. The jeep died and did not want to start. Would crank, but not turnover. Waited 20 mins, and did not start. Figured it could be fuel related due to hill, rolled to a more flat area, and started right away. 20 mins later, stopped on another small incline, turned off jeep, and did not want to start again. Pushed to more level ground and started within 5 mins. No problems after. Drove home 200+ miles on the interstate and made it home fine.

Yesterday, I took the family hiking. Drove 40 miles to beginning of dirt road, and this time the jeep just died while driving. Pulled over where it was pretty flat, let cool for 20 mins, no start. Rolled back to where I had nose pointing down hill. Waited 5 mins, and it started and ran perfect rest of day.

I had at least half tank both times. Temp has always been right around 210.

I've owned jeep for 7 months, and never had any problems on the street. I drive it almost daily. I had put about 500 street miles since last incident.

I will check fuel pressure, and it could also be CPS, but doesn't makse sense it's driving fine otherwise, does it? Weird coincidence?

tjwalker

You are suffering from a "thermal" (heat related) failure of some sort.

The primary suspects for the 4.0 are (in this order) crank sensor, ignition coil and camshaft position sensor.

Testing can be helpful to isolate, but MUST be done while the engine doesn't start. Testing when the engine runs will most likely yield values that are in spec.

djlarroc

Hmm.. that could be a little tough.

Are you saying thermal failure because of low speed? both times it died, i was actually going about 20+ mph.

After the jeep died yesterday, i could hear some sound in the gas tank. almost like a slight pinging.

djlarroc

put 60 city miles in the last 2 days with lots of hot starts. no problems

djlarroc

700 miles later jeep left me stranded again on the trail.. for about 25 mins.

this time i checked spark, and none at plug wire, nor distributor. 15 mins later, no start. 20 no start, 25, it starts.

wiggles

Sounds like the coil then to me but its weird that its so random

tjwalker

You are just going to have to start replacing parts with this random/intermittent nature.

My gut says crank sensor because it is the most common to fail because of heat.

djlarroc

thanks guys. i'm afraid thats what i will have to do.. will start w/the cps.

djlarroc

took a trip last wknd.. seemed like it worked. *fingers crossed*

offroadordnance

Sounds like maybe a loose connection. Did you wiggle test the coil and sensor connectors? Grounds all clean and secure?

ZINGGG

Did you replace the CPS?

MtnHermit

Be sure to check your rear wiring harness, common defect in 1997 XJs. Here's mine from my 1997 XJ:

Here's my original photo and you can make out the manifold mushed into the wire harness:


This closeup makes it very clear:


Simply moving the wire harness from this pinched location eliminated my misfire.

djlarroc

cool! thanks guys.. if it dies on me off-road again, that will be the next step.

i replaced the cps, and it did not die on the trail last wknd.. hoping that was it.