Hey guys, this is my first post so forgive me if this is not the right place to post questions like these. I have an 06 Mustang GT with a super chip, k&n intake, and axle back flowmasters. The car only has about 20k miles and I baby it. Yesterday my engine light came on so I went to advance auto to get it checked and it came up with codes P0174 and P0171 saying I'm running lean. I figured it may be the O2 sensor but at only 20k miles I don't see how that could be. Has anyone had this problem before?? Also fyi, I put the few mods I have on about 8 months ago.

 

Check to make sure you CAI has not slipped loose.
Most lean codes caused by air getting in after MAF.

Bad O2 sensors usually cause rich codes because
computer defaults to rich setting to protect engine.

 

+1 right on the money.

 

Another +1 on a loose fitting. Aftermarket CAI's can be a bit notorious for a clamp coming loose and allowing air in-leakage. It COULD be the tune if it just started happening with colder ambient temps IF the tune was on the ragged edge to begin with. Axlebacks (and catbacks for that matter) won't cause you to throw a code, nor do they provide any performance increase; only sound.

Dump the superchip and get some custom tunes from Brenspeed. I think you'll notice a distinct improvement in performance.

 

Thanks guys, Ill check it out once i get out of work. Something else I have noticed is that I can hear gas in the tank sloshing around. I figured it might be that the gas cap was loose and letting the pressure out of the tank but i checked and i can still hear it.

I'll look into the Brenspeed, i got the the Superchip for free from a guy i know that works there.