Rough idle after short shuts downs

mgroeger

TJ Enthusiast
Joined
Aug 24, 2018
Messages
807
Location
Hurricane, UT
This just started happening a few days ago. The Jeep is running great, idles smooth, no problems. I shut it off, go run in a store, come out around 5 or 10 mins later, fire it up and it idles like crap. I goose it a little and it sounds like crap, almost like it's running on five cylinders. Then if I let off the gas (or sometimes just start driving it) it smooths out back to normal.

The PO did say that since these things get so hot under the hood that the fuel rail can actually develop vapor bubbles in it and they will clear out shortly after being started up.

Any ideas?
 
It probably is running on 5 cylinders...in a way. It sounds like you have a case of "heat soak" which is a common problem with the TJ with the 4.0L. What happens is that heat from the engine rises up and heats up the fuel injectors (the usual culprit is the #3 [third from the front]) and that causes a case of vapor lock in the cylinder; starving it for gas. Until the injector runs enough gas to cool down, it will run like crud but, once it does, it's all good again.
It's a fairly easy fix...let me see if I can find a link to a video.
 
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Here's some pics of my "fix". I used some heat shield sleeving from DEI that I picked up at my local Advance Auto Parts store. I also got a brand new Jeep 4.0L heat shield because mine was pretty well fried (most of the fiberglass was gone). I used high-temp "copper" RTV to seal the edges of the sleeving and the shield so they would not age like the ones I replaced. I have more pics if you would like.
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Here's some pics of my "fix". I used some heat shield sleeving from DEI that I picked up at my local Advance Auto Parts store. I also got a brand new Jeep 4.0L heat shield because mine was pretty well fried (most of the fiberglass was gone). I used high-temp "copper" RTV to seal the edges of the sleeving and the shield so they would not age like the ones I replaced. I have more pics if you would like.
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LOL!!!!! I just saw your name... TJ Hunnicutt. GOOD ONE!
 
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Here's some pics of my "fix". I used some heat shield sleeving from DEI that I picked up at my local Advance Auto Parts store. I also got a brand new Jeep 4.0L heat shield because mine was pretty well fried (most of the fiberglass was gone). I used high-temp "copper" RTV to seal the edges of the sleeving and the shield so they would not age like the ones I replaced. I have more pics if you would like.
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What are the odds the Mopar heat shield can be installed without removing the injector system?
 
And this happens more often when it's cold out? (Serious question) It would seem more likely to happen during the summer months.
Mine will get a heavy gassy smell if I start it up for only a minute or two and then shut it down (before it gets up to running temp) and then restart within 5-10 min. Like a carb with too much choke. Summer or winter. Ideas?