4.0 shutting off

WICKED

Active Member
Joined
Jan 23, 2008
Location
Charlotte
Xj 4.0 shuts off after about 1-1/2 hours of trail riding????? Running perfectly fine the whole time then just dies. Not over heating all guages good no cheack engine light. Let it sit for about 45 minutes and it fires right up and runs perfect. Anybody have this problem before. Any info is greatly appreciated. Thanks guys.
 
had this happen to my girlfriends jeep, ended up a coil or plug wire was breaking down under heat/load. did tune up fixed right away
 
Had a rig with same problem. Turned out the exhaust was too close to the fule lines on the frame rail and it was vapor locking.
 
Thanks to all that are offering advice. Its not the coil, plugs, wires, or crank sensor. All that has been replaced. JC, I will investigate the exhaust and fuel lines. Thanks. And yes OBD1
 
You can't rule out faulty parts just because they were replaced recently. I've been doing mechanic work for most my life and over the years I have gotten several parts from different stores and had them bad right out of the box. Especially electronics.. I was only a Jeep owner for a season so they aren't my specialty, but I do know your symptoms can be easily related to an ignition module/Igniter.

If you can't figure it out, you should keep a plug wrench with you in the truck so as soon as it shuts off you can hop out and check to see if you've got spark, you can also use a key or something small to depress the schrader valve on your fuel rail to verify that there is pressure to it. Once you verify whats missing, which will most likely be one of the two, fuel or spark, you can then go on to the next step of the diagnostic process and move to whats first in line of which one you're missing and start testing stuff. Its a pain, but thats why shops charge big dollars for diagnostic work, tedious, and very few people who can do it effectively. You oughta' be able to look up testing procedures and instructions on how to ohm stuff out yourself with a multi meter.


EDIT: also I just thought about my LT1 Z28 with the opti spark unit, which was a digital eye in the dizzy that read a slotted wheel for cam/crank position, and it acted exactly the same as your Jeep when it went bad, and I think that 4.0 Jeeps have a different but similar setup contained within the distributor too. Might wanna at least try the two answers you got that were the same, seems its half way common.. And like I said, if it came from a parts house and not the dealer the probability of it being bad or going bad really quick is a lot higher.
 
if you've already been to all these parts, look at the plug from the engine harness where it goes into the engine computer-these are bad about working loose and the connector pins working loose, especially when they get bounced around off-road. wiggle the plug with the engine running & see if it skips or dies-a big zip-tie around the plug & computer is a good band-aid
 
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