My truck has an error code. I can't remeber what number the code was but it saws " system bank to lean" I thought nothing of it till yesterday I was driving in the mountians and all of a sudden my truck starts to run really strong. Can some help diagnoise this? I understand that at sea level I am running to lean. The truck is a 6 cyl with an open element k&n.

 

mountain vs. sea level would be MAP sensor (manifold air pressure) air is thinner on the mountain. and i hate to say it but you k&n might be at fault. the truck's computer is designed to mix fuel with a certain amount of air that it knows is possible to come through the air cleaner. So if your k&n is allowing in so much more air then the truck is used to, the fuel injectors may not be able to keep up. Unplug your battery and reset the computer, maybe that will help?

 

We don't have map sensors.
The mass air meter - MAF - measures the mass of air flowing through it and uses "look up" tables stored in the pcm to determine how much fuel to provide.
I would start by checking all of the vacuum lines for leaks.
Oiled K&N filters have been known to foul the maf.

 

I'm sure that my k&n has some thing to do with it. Should put an air box on it and go back to stock or is there a way to program my computer to work?