Hello to all , I have a 96 cherokee country with 150k miles it runs like a champ except when I am off roading at higher altitude (3000'+) It will run fine at lower elevation as soon i get up in high elevation on rough roads an start bouncing around it starts sputtering an wants to die. I know it something to do with the pressure in the gas tank but has anyone experienced this? I replaced the gas cap but it still happens, Ive driven at high elevation on highways an it runs fine. Also when i stop an open the gas cap it release all the pressure like a deflating balloon, an then if i let it sit for 5-10min it will fine for a little bit do it all over. Hope this makes sense. Any ideas please HELP

 

non carb, right?

 

Less oxygen at higher altitudes, could mess with your a/f ratios. When the indians used to climb the high altitude mountains they would chew on coco leaves to get their heart rate and respirations higher to counter the lack of oxygen. Hook up an oxygen tank into your breather lol jk I don't know how to help you...

 

reset the cpu when ur up there

 

Any other ideas?

 

The MAP sensor measures Absolute Barometric Pressure and the PCM leans out the mixture based on the signal received.
Thoroughly clean the passages in the TB and replace the sensor if that doesn't fix it.

 

While this is true, its based on true HIGH altitudes aka 15,000+. Your jeep should run fine without any major problems up to at least 14,000. Beyond that I have not been since that is the highest we can get here in Colorado. 3,000 shouldn't be a problem at all.

Check your sensors, I have a feeling something is clogged up and since you are most likely running at lower RPM's while wheeling and thats why it will run on the hwy but sputters on the trails.

 

I drove my 96 Sport XJ from Vermont to where I live in Colorado and never had a single issue due to altitude (or anything else! woo hoo!). This was basically going from sea level to 12000ft in about 2 days. The sensors in the engine detect the difference and adjust the mixture accordingly. If you think the altitude is affecting your mixture, I'd definitely start with sensors, and like the PP said, the MAP in particular!

Another thing I thought of would be if you have a lot of crap built-up in your fuel tank or fuel filter, the rough terrain could be stirring it up. Have you replaced the fuel filter recently? My buddy and I had a problem like this with an old 6V ****** engine that had been sitting for about a decade. Every time we hit rough terrain, it would shake new stuff loose that had settled in the fuel tank. We pretty much knew that was coming though since it sat for so long. (Went through a million filters after rattling a chain around in it before we gave up and just got a new tank.)