Hi guys, I have a friend who has a 2006 Mazda Tribute 4 cylinder. She recently has experienced a pretty big problem. The idle is very rough after coming to a stop. Also, sometimes when accelerating, the car stutters.

I pulled the code for the check engine light and got:

P0171 - System Too Lean (Bank 1)
http://www.obd-codes.com/p0171

Now according to the link above for code P0171, this could be due to a dirty or faulty MAF. The possible symptoms also match:

"You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration."

We went ahead and went to Kragen and purchased a remanufactured mass air flow sensor and installed this, cleared the code and took it for a test drive. We experienced the same exact symptoms right away.

Anyone have a similar problem? Could there be another reason why the system is running lean?