Anyone have issues with their JK stalling at high altitude (above 13K feet)? This past weekend I had my 2011 JK stall a number of times while driving above 13K feet. Had to work my way down the mountain in neutral with the parking break and no power steering. Once I got below 11K feet the engine started up just fine and I haven't had any issues since. This wasn't the first time I have been above 12-13K in Colorado and I've never had issues in the past. I've been searching the internet and this forum for answers, but everything I've found states newer vehicles shouldn't have an issue with altitude. All I know is that it isn't a very pleasant feeling to have your engine stall continuously when you are out in the middle of nowhere on top of a remote mountain. I've also read the fuel filter shouldn't be an issue either. I do have the EGR check engine light, but not sure if that would cause a problem or not. If anyone has had similar issues and found out the cause I'd appreciate any insight into the problem.

Jon

 

did you have it in 4-lo? what kind of terrain; mud, rocks or steep climb? What gear were you in?

 

I've been in he highlands of co a few times now with no issues. Right around 11- 13k.

 

junoh,

I had it in 4-lo working our way slowly along a flat shelf road after a small incline. There was no mud or rocks and luckily it first stalled before we started up another steeper incline around a pretty tight corner. Not sure what we would have done if we had gotten around the corner before it stalled. Tried to restart a couple of times before I was able to get any power from the engine. With a little push we were able to start down the incline in reverse and get to a larger flat area where we turned around. It stalled multiple times again as we were turning around and this happened in both drive and reverse while turning in 4-lo. After turning around we had about a 100 yard flat area where we were able to use the engine enough to get us started down a few extremely steep switchbacks and it stalled here a couple of times as well. After the steep switchbacks we had a few longer, gradual switchbacks so I left it in neutral and coasted down to about 11K before we could get the engine to remain started. After that we had no issues at all. When we could get power, I had to give it quite a bit of gas but then it would bog down and stall. Each time I would only have about 2-3 seconds of power from the engine.

Checked the air filter and it was fine. After a little research all I can come up with is a bad batch of gas with extremely poor timing. It's my understanding a newer vehicle should compensate for altitude and the JK fuel filter shouldn't be an issue. The guy with me said it reminded him a lot of a clogged fuel filter. I'm tempted to drive up Mt. Evans (14K) which is at least populated and paved to see if I have any more issues.

 

Hey,

I've had my 2012 over 12.5K more than 40 times, and never had an issue. Bad gas maybe?

 

Yeah, I would guess bad gas. The Mass air flow meter is what handles the altitude changes. Are you running a stock air filter or a K&N? I ask because filters like K&N use oil to trap dust and dirt, and they can transfer oil to the wires on the Mass Air meter and that too would cause an issue at altitude.

 

Very interested in your findings... as we go to Colorado all the time..
What octane of gas are you using.. I know when I go into Colorado or Utah I do mid grade since I have found my Jeep hated the low octane, it never stalled but it missed some... that's when I started putting the mid level in and it improved right away... hopfully it's just a bad gas, rare moment.. this was with my 2011 JK...
driving up to mt evans is probably a good idea.

 

Do you even know what octane is used for? It's a knock inhibitor. There is less potential energy in higher octane than there is in lower octane. Knock is caused when the piston travels upward and the compression creates extreme heat and causes pre-detonation. The reason why we don't have 93 octane in Denver is because our air is less dense to start with. There is less chance of pre-detonation here so less octane is needed to prevent that. Now if your at 13K above sea level, the octane level needed to prevent knock is going to be around 70 octane. The 85 octane in the fuel is over kill at that point so going tp 87-91 for high climbs is only going to kill the engine performance.

And BTW, I've read that the Mid grade gas is the least selling gas so the tanks will have a higher chance of having old gas or water in the tanks compared to Low or High octane gas. Good possibility is he got gas with a high ethanol content(more than 10%) that the jeep just didn't like.

 

One of Chrysler's OS weaknesses is they do not run MAF sensors. A MAF sensor allows the engine to be fueled based on actual airflow, not calculated. As altitude changes the MAF sensor will pick up the difference in air density better than a MAP sensor which is based on intake manifold vacuum. Another benefit of the MAF sensor is in the event of a failure it will revert to a speed density mode and use the MAP for fueling. MAF sensors are expensive but do deliver a more stable operating range.

Using the correct fuel and allowing the OS's adaptives to correct for environmental conditions is important. In the old carb days manufacturers produced high altitude vehicles which dealt with the thinner air better. Various electro-mechanical devices were added to carbureted vehicles to help deal with altitude changes.

In the 80's some manufacturers used a separate MAP and Baro sensor, this way the Baro sensor would tell the OS what the current air density was. To save some dollars most manufacturers removed the Baro sensor and combined it with the MAP sensor so when the ignition is switched on a Baro reading is taken and stored for reference. This worked well unless the vehicle changed altitude greatly in the same ignition cycle.

So take a little tip from the 80's owners manual. If you change altitude more than 3 or 4,000 feet power down your vehicle and then restart, it may help get a more accurate Baro reading. At very high altitude it may benefit to clear your adaptives and allow them to relearn at the new altitude.

Modern OS's use calculated Baro readings as the vehicle runs down the road. Using predetermined tables which look at MAP pressure, O2 feedback, ECT and other variables the Baro reading should be close in the calculation. It's never a perfect world and the JK is stuck without a MAF sensor or independent Baro sensor so it will remain susceptible to rapid altitude changes.

 

I always use 85 octane. As stated earlier in the thread, I'm pretty sure higher octane is worse at altitude. Also have the stock air filter. Guess I'll chock this one up to a bad batch of gas. Thanks for all the inputs, I appreciate it.