I recently installed a K&N air intake on my 04 GMC sierra, my check engine light has since come on, and when i had the code pulled its PO174 and PO171, in other words bank 1 and bank 2 are running to lean. I'm getting to much air and the computer is not compensating by adding more fuel. When the truck idles you notice its not a smooth idle other wise it drives great. I've taken the intake apart, cleaned the MAF sensor, reinstalled the intake and unhooked my battery allowed it to sit for half hour, had the codes erased from the memory and the truck ran great for about a day, and then the check engine light came back on and the same two codes showed up, and the idle isn't smooth. I am not sure what else to do besides uninstall the intake and put the factory back on which i'd rather not do. any help would be greatly appreciated. oh and another thing I also have a throttle body spacer which i've had on there for a year or so. The truck only has 60,000 miles i do not believe that the MAF sensor is bad, especially since it was working perfectly fine prior to installing the new intake. thanks

 

I don't know if the set-up is the same (Silverado and Sierra), but when I bought my 04 Silverado it had a K&N w/ TB spacer on it.
I had the exact same problem- kept throwing codes, and not the best idle.
But I found that my TB spacer would not allow the tube to sit flat against the Throttle body, and the tube would actually slip off nearest the TB, at the bottom. It wouldn't be visible from up top.
I would have to re-attach the tube and I had to do this especially after hard acceleration. The trick was not too overtighten the tube.
I ended up taking off the TB spacer.
Once I removed the TB spacer, all my problems went away- no more slipping off the TB, and no more codes, no more worries...And had the same performance.

I'd say try that, instead of the intake.

Good luck!

 

Sell that TB spacer to some other sucker - it's doing you no good.

 

You had to have messed up your MAF or something. Adding a K&N intake is not going to make your truck run bad unless you messed something up. In perfect conditions you'd be lucky to gain 10rwhp

 

Yeah I'd check to make sure there are no leaks anywhere and that everything is tight. Everyone bashes the TB spacer but I've always gotten a little better mpg's witht hem, never a power gain but it was worth it.

 

sounds like you have a leak somewhere in the tubing... Your sucking in Un-metered air, which is causing your fuel trims to max out... It usually take a little while for the trims to max out, and when they do it throw a code... IMO go over the entire intake again and make sure you don't have any leaks...