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Unread 03-21-2013, 10:55 AM   #1
c0r3f1ght3r
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Join Date: Dec 2012
Location: Columbus, GA
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Jeep stalls while driving, engine restarts

I've been having this issue with my 96 Grand cherokee laredo, 4.0, auto. I will be driving down the road and randomly the engine will restart. All the gauges reset, and sometimes it will do this as I am slowing down or just sitting at a light, and sometimes it just complete dies.

So far I have replaced the CPS twice, second time I got mopar sensor, and this didn't help at all.

Then I replaced the first O2 sensor, and cleaned the IAC along with the throttle body itself, there was a lot of carbon build up in there... I made sure the IAC was pretty much spotless. The jeep ran with no issues for about two days and then started stalling again.

I have noticed that when I have the car running and I start wiggling the computer in the engine bay it will reset. I have been told I may need a new computer...

At this point I really don't know what to do with this car, because its not really worth fixing... they only sell for what 1200$ in good condition now.. I wonder if replacing the computer with one off ebay would help the issue. Do they need to be programmed or anything?

-Thanks

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Unread 03-21-2013, 11:24 AM   #2
Uniblurb
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1996 ZJ 
 
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Location: Central, Ohio
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Read through the below excellent thread by ZeeJay and pay close attention to #1 (The Brain) and #2 (Grounds). Just the fact you can wiggle the connectors on the PCM and it will reset itself indicates you have a bad connection or something's amiss in the unit itself like bad solder joints. Follow the instructions in the thread for cleaning and maybe installed wire ties around the connectors as a temp fix. Good luck.

http://www.jeepforum.com/forum/f13/1...talls-1407423/

BTW, a bad engine ground by the coil took out 2 PCM's along with the crank sensors on my 96 4.0. This cable on one of the coil studs grounds the PCM which in turn grounds all the sensors and it's a vicious circle.
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96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 93 4.0 XJ (spare), 96 4.0 XJ (son's)

-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
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Unread 03-21-2013, 11:56 AM   #3
c0r3f1ght3r
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Quote:
Originally Posted by Uniblurb View Post
Read through the below excellent thread by ZeeJay and pay close attention to #1 (The Brain) and #2 (Grounds). Just the fact you can wiggle the connectors on the PCM and it will reset itself indicates you have a bad connection or something's amiss in the unit itself like bad solder joints. Follow the instructions in the thread for cleaning and maybe installed wire ties around the connectors as a temp fix. Good luck.

http://www.jeepforum.com/forum/f13/1...talls-1407423/

BTW, a bad engine ground by the coil took out 2 PCM's along with the crank sensors on my 96 4.0. This cable on one of the coil studs grounds the PCM which in turn grounds all the sensors and it's a vicious circle.
I just stumbled onto that thread and thanks. I'd like to also mention that the CEL light comes on, but when it restarts the light goes away. I tried to have a mechanic check it but he said the computer must be resetting the codes.
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Unread 03-21-2013, 04:17 PM   #4
dean477
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1998 ZJ 
 
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Location: Los Angeles, California
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Ive had this issue for a year and a half now. Zip ties worked for me for awhile but they eventually stopped working consistently and got worse over time. It got pretty bad about two months ago with the zip ties and i was stuck trying to start it for 30 minutes at 2 am in a residential zone. I kept having to try to start it a few times then pushing it down the block so i wouldn't piss off the neighbors. anyways, im a firefighter/emt and dug through my bag and pulled out my blood pressure cuff. I placed the cuff in between the coolant reservoir and terminals on the computer, inflated it to 80 and haven't had a single stall in over 2 months.

A quality blood pressure cuff that doesn't loose too much pressure will cost you about $20. I re inflate mine every week or so to the range of 60-100 mmHg. Try it, it works!
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Unread 03-21-2013, 06:44 PM   #5
ZeeJay1997
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Be sure to check/clean contacts in the connector (see dirty dozen) before you condemn the PCM. Good luck!
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Unread 03-23-2013, 07:40 PM   #6
radiodoctor
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Quote:
Originally Posted by dean477 View Post
Ive had this issue for a year and a half now. Zip ties worked for me for awhile but they eventually stopped working consistently and got worse over time. It got pretty bad about two months ago with the zip ties and i was stuck trying to start it for 30 minutes at 2 am in a residential zone.
I could touch the ECM connector closest to the engine and make the engine run or fail. I used a rope to hold tension on the connector to get home.

I found a Parts Grand Cherokee on Craigslist that had the same ECM part number. I bought the ECM and installed it and the Cherokee fired up with half-revolution crank and has been running fine ever since.

I will probably resolder the pins on the original ECM just to have a spare.
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