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i recommend turning O/D off when driving in the hills/mountains
 

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Your computer should cover the oxygen content problem.
A good shop should be able to hook it up and give a read to make sure things are working right.
Codes and lights do not cover all problems.
Plugs? Fuel filter? Fuel pump? Air filter?
 

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Your computer should cover the oxygen content problem.
A good shop should be able to hook it up and give a read to make sure things are working right.
Codes and lights do not cover all problems.
Plugs? Fuel filter? Fuel pump? Air filter?
The problem is not oxygen content. Actually, oxygen content remains the same at any elevation. The deviation is in the fact that the air itself is thinner which in turn means less oxygen as a whole and not a lesser oxygen content. So the computer won't adjust the mixture because it's still reading a 12% oxygen content in the air-flow (I made up that number just as an example). The problem is, the air-flow has diminished to 60% of what it would be at sea-level. Or worse.

Below 5500ft, the air pretty much remains the same but once you go beyond 5500ft., the air really begins to thin out. I can't find my info I used to have on the ratio of elevation gain to air content.

Don't mistake Duke though, he is right in what he is saying. The ECU "should" adjust for a change in mixtures but elevation doesn't actually cause a change in mixtures. It's a popular misconception.
 

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Im having the same issue with my 2003 se. Drives perky around town and on highway but on hills even at sea level mine slows to a crawl. The steeper the incline the worse it is. I had a to pull to the side to let a few cars pass me on a mountain pass as i was just in their way. I was thinking it could be air intake or possibly wrong size tires. Downshifting bares no significant changes. Ive got a lot of business up north in the mountains but ive been putting it off bc i cant figure out this issue.
What would disconnecting the batt improve? (green horn)
 

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Im having the same issue with my 2003 se. Drives perky around town and on highway but on hills even at sea level mine slows to a crawl. The steeper the incline the worse it is. I had a to pull to the side to let a few cars pass me on a mountain pass as i was just in their way. I was thinking it could be air intake or possibly wrong size tires. Downshifting bares no significant changes. Ive got a lot of business up north in the mountains but ive been putting it off bc i cant figure out this issue.
What would disconnecting the batt improve? (green horn)
Have to wonder about the fuel "tilt" in the gas tank effecting the fuel flow when you go up an incline. Does it loose power when you go down a hill? Ever change the fuel filter or gas cap?
 

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Have to wonder about the fuel "tilt" in the gas tank effecting the fuel flow when you go up an incline. Does it loose power when you go down a hill? Ever change the fuel filter or gas cap?
I havnt really thought too much about it i had a rodeo and a pathfinder and never felt the same lack of power im feeling here. And were talking about the same roads im well travelled on. Im the 3rd owner of this xterra and their was no record on what was worked on i was told it had regular maintenance and no mods other than tires being bigger than stock. So far the codes that pop ar PO505 which is engine idle. As well as PO138 which is rear o2 sensor remaining high. Ill be honest boys im not sure where to start on this like i said im a green horn here! Im willing to take any consideration =)
 

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I havnt really thought too much about it i had a rodeo and a pathfinder and never felt the same lack of power im feeling here. And were talking about the same roads im well travelled on. Im the 3rd owner of this xterra and their was no record on what was worked on i was told it had regular maintenance and no mods other than tires being bigger than stock. So far the codes that pop ar PO505 which is engine idle. As well as PO138 which is rear o2 sensor remaining high. Ill be honest boys im not sure where to start on this like i said im a green horn here! Im willing to take any consideration =)
I'm serious about the fuel filter. Cheap maintenance. Low risk $$.
 
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