I have a 2011 Jeep JKU Rubicon with a stock motor that I am having an issue with. At high altitude (above 11,500') my JK will shut off almost like it runs out of fuel. It will restart after cycling the key for a few seconds, almost like it has to reprime the fuel. It will run for a little while and shut off again. This happens multiple times until I start to descend in altitude. I have already replaced the MAP sensor...no change. any ideas? Oh and when it happens, it does not throw any codes.

 

I have no idea, but I wonder if it would help if while at high altitude, you disconnect the battery for awhile.

 

11500ft is about it for naturally aspirated vehicles. Need a turbocharger at those altitudes. Air is thinner and fuel can boil in the line causing vapour lock which will go away once the engine cools a bit. Try loosening the fuel cap off when it does this and put up with the CEL just to find out if it works.

 

Fuel boiling in the lines even though the Jeep's temp is okay?

 

We just did a week trip 4 wheeling in the San Juan Mountains out of Silverton Colorado. Several passes up to 13,000 ft and never had a problem with my 2012 JK Pentastar. There must be something else involved.

 

I've been over about every pass in Colorado in a 98 TJ, 10 JKU, and 16 JKU. Never had any engine issues with any of those 3 different engines. Fuel injected engines shouldn't have issues at 11,500 for sure.

 

The fuel can boil if the tank pressure drops. Check the fuel cap etc. What you describe is a classic for fuel starvation or boiling, Has nothing to do with engine temps.

Just a Note: A good friend of mine was the NATO test pilot for European forces (except the USA) in Europe on F-104 Starfighters. He wore a pressurized space suit in a pressurized cockpit simply because his blood would instantly boil at 80,000ft if the cockpit de-pressurized without the suit. Same situation with your fuel possibly. Friend was also 19 year old flying P51's in combat in 1945. He has had quite a life and is still alive.

 

That's rediculous, many people, myself included frequently drive above that altitude with no issues, even dare I say it, with a carb

 

And this helps me how?

 

Just to clarify - my point should not say the motor is useless above these altitudes but it sure is down on power (I used to fly and at 12000ft I only had 55% of my total HP). The kit plane world record holder for NA airplane was a guy from Toronto at 26,000ft on an NA engine. But the issues I state are good to check as I say again, it sounds like your engine is starving for fuel. So I would look at the fuel delivery system and also perhaps if you can try and have a scanner with you to take some fuel pressure readings when the issue arises. There is nothing wrong with the design of the Jeep you just have something wrong and have to find out what it is. If you know anyone with programs like HPTuners or similar they have a live scan function that will read your system in real time.