Crush11

All:

I'm hoping someone has some insight on this for me. Each time this winter I have taken my 2011 JK Unlimited into the mountains I have had serious power issues. Once the vehicle gets above about 6000 ft it struggles to maintain a highway speed. And once off the highway on other paved roads, the engine revs way too high - around 5k - to maintain 40 mph on a slight grade.

There were no signs of overheating, although the engine seemed to be running too hot.

I removed and replaced the gas cap at about 8000 ft, and that had a slight impact, but not enough. The air filter is brand new, so I wouldn't imagine that breathing would be a problem.

Obviously at lower speeds, it isn't an issue, but sometimes you need roads to get to where there are no roads...

Has anyone else had this issue? Any thoughts on a fix? If this is just how its going to be, this is a deal breaker for me.

101gargoyles

5k rpm at 40 mph = trip to mechanic...dealbreaker

Joe_B

Any vehicle at altitude will suffer power loss. The only way to fix this problem is forced induction or a LS and Hemi swap lol. Tuners and exhaust won't really do much either if you're constantly driving around the mountains.

If you have an auto, shut the OD off and put the jeep into 2nd gear. It will help maintain speed and limit gear hunting. Saving your tranny.

Driving to Moab last year from Toronto we had to cross the lovely Rockies of Colorado in our jeeps. Even with having the jeeps geared to run 35s and 37s, the guys with auto tranny's hated it lol. But the jeep will do it and it will be fine.

tjkamp

Supposedly overtime the computer will adjust the air/fuel mixture some to make it a little better, but that will take time and require you to stay in the mountains.

Crush11

Thanks Joe_B.

We ran with the OD off, and it helped, but made the drive painful in other ways. Getting passed by four door Hyundais is demoralizing.

The engine performance surprised me, so I just may end up take the Tahoe to the higher altitudes and leaving the Jeep in the desert where it seems to be happy.

Sadly, I have considered the Hemi - a buddy of mine wants to drop in a diesel for me - I'm not sure I want to completely change the mechanics in the whole vehicle.

ronjenx

The computer makes those changes several times per second.
Normally aspirated gas engines lose about 3% - 4% of their rated hp with each 1,000 foot gain in altitude above sea level.
So your 202 hp 3.8L engine will produce only about 147 hp at 8,000 feet. That's a significant loss.
It gets worse if the engine is already struggling for other reasons.

Rob 12B1P

OP are you talking about pulling grades at 6000 feet or level ground at 6000ft? What size tires are you running and what gears are you running in the diffs? The 3.8 will never throw you back in your seat but you shouldnt be struggling that bad if you are set up correctly.

Ncb

I made a trip to Eagle yesterday from the Denver area. Vail pass is at 10,600 and the JK is no rocket ship on the bigger hills. There were a few places I had to hit fourth to maintain the speed limit. You will feel considerable power loss at altitude plus steep hills. I have 4.88 and 35s on my 2009 with manual transmission. With out boost it will be a slug in the mountains.

My WRX with minor mods would go 75 mph in fifth gear the whole way. Miss that car for mountain trips.

CombatDiver

I have to agree with many posts that at altitude my Jeep has seemed a little sluggish (slow to accelerate). It has been able to get to and maintain the speeds I have wanted to (speed limits reaching 85 mph) just doesn't do it with the same gusto as it does at lower altitude. I have a buddy with a Tahoe and he would love it if it could out perform my Jeep but the truth is it hasn't yet. While there is a variety of variables that goes into something like this apart from that which you already mentioned I would wonder if the oil thickness might also contribute (making it better or worse). I think I'm not alone in saying a Jeep Wrangler is like having a child, you constantly worry about it but in most cases it will turn out just fine.

Desert Crawler

I live at 6200 ft and regularly travel a pass that is 8900 ft. While it doesn't compare to our BRZ, it travels up all of the sierra passes at the speed limit or greater. (3.6L, 6-speed).