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Unread 08-29-2013, 11:32 AM   #1
MeWJWifeZJ
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1996 ZJ 
 
Join Date: Sep 2008
Location: Richfield, Minnesota
Posts: 518
96 ZJ Just stops running.

If I start my ZJ in the driveway it'll fire right up but without warning it'll shut off. It could be 15 seconds, it could be 4 minutes later. Running down the road it will shut off during acceleration, while cruising, at a stop sign it doesnt matter. When i'm driving it, the gauges fail and fall to empty on the gas gauge, zero volts, zero oil, zero temp but the tach and speedometer freeze where they were, most of the time they recover and the engine will start running again in a matter of seconds all on it's own. I'm confused as to what it could be. I have new Mopar Crank and Cam sensors, O2 sensors, the grounds at the engine block, next to the battery and the main cable ground have all been cleaned to bare metal and re-installed. The IAC is a new Mopar piece, the TPS checked out ok, the coil wires are routed properly and the coil is not cracked. The computer harness doesnt seem to affect anything as I can grab the harness at several different places when the ZJ is running well and shake, twist, bend, and move it with no issues. The connectors at the computer are solid and nothing changes when I attempt to move those either. I've swapped around the relays to see if I had a bad one, but they all test good too. Fuses are not popped either. I'm at a loss. It's the Wife's vehicle and she wont even drive it until I get it fixed. Ideas?

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Unread 08-29-2013, 01:51 PM   #2
Oldfrog
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1997 ZJ 
 
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Any codes?
Coil check out?
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Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 08-29-2013, 02:09 PM   #3
MeWJWifeZJ
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If it ever does send a code, it gets wiped out when the gauges go flat and the truck dies so nothing is ever stored. Coil checks good. Tried disconnecting the front O2 sensor and it ran much worse which tells me that it's doing it's job too.
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Traded away the WJ to get a commuter

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Unread 08-29-2013, 02:15 PM   #4
PolkaPower
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1998 ZJ 
 
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Crank sensor?
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Unread 08-29-2013, 02:18 PM   #5
MeWJWifeZJ
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1996 ZJ 
 
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Brand new Mopar unit. Last one in the state.
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Praise to a Child is like Sunlight to Flowers

Traded away the WJ to get a commuter

We finally got another Jeep after 5 years without. Too bad it's ALL stock.
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Unread 08-29-2013, 06:39 PM   #6
ZeeJay1997
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1997 ZJ 
 
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It sounds about like the first bad PCM i had. Mine didnt shut completely down unless it was idling or coasting. if I was cruising, it would just jerk a knot in my butt. Your description of the gauges and PCM resetting is deja vu all over again. Mine would also stall when cold if I tapped a certain place on the case.

Polka is correct that a crank sensor can mimic these symptoms.

I would give the PDC a once over as described in the link below and consider replacing the PCM.
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Unread 08-30-2013, 01:30 PM   #7
Oldfrog
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1997 ZJ 
 
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Quote:
Originally Posted by ZeeJay1997 View Post
. if I was cruising, it would just jerk a knot in my butt.
Mine did that 2 days ago. I hate that feeling, so I bought a new coil and tossed it in the back.

Yesterday, I wiggled the coil connector and all was well for a whole day. Looks like I'll once again swap the coil this weekend and work on that connector.

Before I die, I'd like to get my hands on the skinny necks of the electrical engineers who worked on the ZJ design.
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Cajun Recipes and Fishing tips

Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 09-01-2013, 08:16 PM   #8
MeWJWifeZJ
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1996 ZJ 
 
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So tonight I completely disassembled the PDC and cleaned each terminal as well as cleaned off each termial on every relay, and fuse with emery cloth. I changed the crank sensor, cleaned the battery terminals and terminal clamps and verified all connections in the wiring were clean and tight. After it sits for a day or more, the first time the key is turned on, there is no CEL and the fuel and volt gauges dont respond at all. If I leave the key on, after abour 30 seconds the PDC starts freaking out and relays go clicking on and off. I can't isolate which ones but once they start clicking, the fuel gauge activates, the volt meter responds. if I leave it run in the driveway, the relays starts clicking when it stalls too. The only code is P1391 even with a 2nd new CPS and a new Cam sensor.. still stalls at random. No shorts in the fuel injector wires, moving the wiring harness has no effect.
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Traded away the WJ to get a commuter

We finally got another Jeep after 5 years without. Too bad it's ALL stock.
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Unread 09-01-2013, 08:21 PM   #9
Oldfrog
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1997 ZJ 
 
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Location: Louisiana/Texas
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Dont be insulted, but when one of my batteries died, it freaked everything out, as you just described.
Load test it.
__________________
Cajun Recipes and Fishing tips

Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 09-01-2013, 09:26 PM   #10
ZeeJay1997
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And check disassemble the grounds on the block and fender, clean them, put them back on. Need to eliminate all the variables such as battery and grounds.

Sounds like a bad cap in the PCM.
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Unread 09-01-2013, 09:59 PM   #11
ZeeJay1997
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1997 ZJ 
 
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here's an afterthought, if the crank sensor signal is absent, the PCM doesnt send the relay grounds.

It will not crank or run without crank sensor signal.
It will run but not crank without cam sensor signal

So the as the code suggests, and intermittent crank sensor signal is suspect. Since you have changed the sensor already, it would be a good idea to pull the black connector off the PCM and check pin 18. it may be pushed back. The sensor ground is furnished from the PCM on pin 4. it splices in the main engine harness near the injector wiring breakout.

Also, remove the TPS connector and turn the key on. Check for 5V between the two outside sockets on the connector.
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Unread 09-02-2013, 12:14 AM   #12
Jayzer97
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1997 ZJ 
 
Join Date: Sep 2013
Location: Fresno, California
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Mine kept dieing on me also but when I changed the charge temp sensor on top of engine behind alternator ...not the coolant temp sensorbut will be good to replace also ......try that out Kk ...
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Unread 09-02-2013, 07:15 AM   #13
ZeeJay1997
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Quote:
Originally Posted by Oldfrog View Post
I'd like to get my hands on the skinny necks of the electrical engineers who worked on the ZJ design.
lol, pencil neck geeks!
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Unread 09-02-2013, 08:44 AM   #14
coralman
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1998 ZJ 
 
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Wasn't there pronlems with the harness breaking or rubbing through at that point also Zee?
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Unread 09-02-2013, 10:03 AM   #15
ZeeJay1997
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You're right Coralman. As the wire bundle turns around the back of the head, there is a stud standing up that causes chaffing problems.
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