YJ 4.0 shuts off randomly, won't stay running. - JeepForum.com

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post #1 of 6 Old 06-16-2009, 04:50 PM Thread Starter
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1995 YJ Wrangler 
Join Date: Jun 2008
Location: Jersey
Posts: 45
YJ 4.0 shuts off randomly, won't stay running.

1995 YJ 4.0

Noticed this problem after rebuilding the engine. After about 90 miles on new motor this problem started. It is intermittent, some days I'll get by fine, others it kicks in after driving 1/4 mile.

Jeep engine shuts off randomly in the middle of driving, no stutter, just shuts off completely. Electrical stuff still on, radio, speedo, etc, but no engine. After pulling off the road, it cranks and starts, but shuts down after 2 or 3 seconds. Sometimes it stays runnning longer, but ultimately shuts off. Does not matter what position the throttle is at, it shuts off.

It is not a starving shutdown, its computer controlled shutdown, as if I turned the key off. At first after cycling the check engine light codes, it came up with 54 - Cam Pos Sensor. Replaced that, problem still exists however that code no longer shows up.

Replaced CPS (crank) but problem still exists.

Any ideas? I don't trust it to drive anywhere, as it shuts off randomly and leaves me in the middle of the road.

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post #2 of 6 Old 06-16-2009, 05:54 PM
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1991 YJ Wrangler 
Join Date: Feb 2005
Location: Lake Havasu City, AZ
Posts: 614
Check to see if your fuel guage pegs out on full when this happens. If it does you have a bad ground to the fuel pump. The fuel pump and fuel guage use the same ground wire attached at the parking brake mount bolt.

91 Wrangler 4.0 5sp
8.8 4.10 explorer axle, 33x12.50x15 x-terrains,Rancho 2.5 lift and shocks, Goforit 1" motor mount lift, 1" body lift, sailcloth top with tinted windows
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post #3 of 6 Old 06-16-2009, 05:59 PM
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1987 YJ Wrangler 
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Location: Hernando, Ms
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I fought this problem with a friends 4.0l XJ.
It ended up being the aftermarket coil that was the problem.
I replaced it with a Dealer OEM coil and it has been running fine ever since.

Just another possibility.


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Last edited by zeus87gn; 06-17-2009 at 06:32 AM.
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post #4 of 6 Old 06-16-2009, 06:06 PM Thread Starter
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1995 YJ Wrangler 
Join Date: Jun 2008
Location: Jersey
Posts: 45
Thinking about the coil as being a problem, I'll have to test that out. I wonder if its thermal failure.. have to check it when its hot.

Also, I'll keep and eye on the fuel gauge, but don't think its the pump, as when it dies the fuel rail still has plenty of pressure.
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post #5 of 6 Old 09-10-2009, 08:40 AM
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1977 CJ7 
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Location: ohio medina
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I have a 1991 yj with a 2.5 4 banger and 5speed it whats to shutt off only if you hit a big bump in the road but has not shut down i had a proublem with shutting off and pulled of the road it just crank no strat but let sit for a min. and it fired up i replaced the full pump and still doing it my it is the coil i need help thanks
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post #6 of 6 Old 09-22-2009, 08:17 AM
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1977 CJ7 
Join Date: Sep 2009
Location: ohio medina
Posts: 5
i think i got it the battery negtive cable had one of those repair kit ends on witch are junk cause the coil gets its ground form that cable every time i would hit a big bump the engine would cut out cause it was loose in the clamp on the cable to the battery end
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