Diagnostic question - sudden stalling - Jeep Wrangler Forum

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Old 07-22-2012, 01:56 PM
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Diagnostic question - sudden stalling

2000 TJ, 4.0L, auto, 100k -- the thing cuts out suddenly, with no warning, no sputtering, no nothin' . Happened three times so far; the first two times, I coasted the jeep to the roadside, and it re-started. This last time, it wouldn't start.

It cranks OK, and there's pressure in the injector rail.

I couldn't get it to throw a code on the odometer.

Diagnostic suggestions ?

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Old 07-22-2012, 03:35 PM   #2
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Sounds very similar to what mine did right after I bought it. Had to push it off to the side of the road, as it stalled abruptly as I was slowing down for a stop light. Tried cranking it several times over a 5 minute period, then it started up like nothing ever happened. Luckily, mine threw a crank sensor code pointing me right to the problem. I've seen a lot of posts on here about crank sensors and cam sensors. If I remember correctly, the crank sensor code should set if the ECM sees 3 revolutions of the cam without seeing a crank sensor signal.

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Old 07-22-2012, 04:04 PM   #3
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My guess is your crankshaft position sensor has gone bad. The CPS is what provides the engine's master timing signal and when it doesn't do that, the engine will halt abruptly. There are of course other things that can cause that too but the CPS would be my first guess. The CPS is mounted high up on the driver's side of the transmission bell housing next to where it bolts to the engine.
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Old 07-23-2012, 10:30 PM
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Thanks to both of you.

I had my mechanic go into it today. Unfortunately, the dang thing started and ran perfectly at the shop -- this after a total die-out and no restart on Sunday. I HATE intermittents !!!

Anyway, he found nothing wrong with the wiring (looking for the typical Jeep insulation-chafe, that is). He too was of the opinion that it could be the CPS, so I told him to replace it. I hope that fixes it; I don't like driving around in something that might crap out at any moment.

Interesting thing -- he told me that while his little handheld code reader would pull codes off the engine (nothing wrong, though), the "big" reader in his shop would not. Simply doesn't seem to "talk" with the onboard compuker. So this may not be over.

Again, thanks.
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Old 07-25-2012, 02:03 PM   #5
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I just got done fixing this same problem in my 2000 4.0 Wrangler with 120K miles. I ended up replacing the throttle body sensor, crankshaft sensor, and cam shaft sensor in that order. Bought everything at an autozone parts store for under 150$. Though that did not fix the problem. My problem ended up being a short in a wire above my battery in the engine harness. My battery was not strapped down tightly and the harness chaffed the wiring. Also my cable to the relay box from the battery was not secured tightly causing my jeep to die on bumps and turns. Though crank shaft sensor was the first thing I was told. Those other sensors could cause the same problem if starting to fail. After putting everything in my Jeep runs better than it has in a while.
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Old 07-26-2012, 06:59 AM
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Thanks! This gives me some other possibilities, in case the CPS wasn't the problem. I'll have to check the battery-to-relay-box connection -- although I doubt that's bad, since I've driven this thing over some rough roads and haven't had it sputter.

The battery terminals themselves were wobbly-loose when I got the Jeep, and that created its own set of troubles -- wouldn't crank or start, but the peripheral electricals worked fine.

BTW, it's three days (and counting) since the CPS replacement, and no further trouble yet. (Of course last time it was three WEEKS before it repeated.)

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