I just joined the audi community a few weeks back. I have an 2002 Audi A4 1.8t. I work at a chevy dealership so Audi is completely foreign to me. I installed a new Dv that is a blow off valve/ Dv made by a friends company. I have the blow off blocked off so it is recirculating it back like stock. That was about a week ago and now I have a check engine light code P0171 (engine to lean bank 1). Any ideas on what could be the cause??

 

check the vacuum hoses going into the intake manifold. if that checks out its probably your MAF. you could try cleaning it, if that doesn't work, find another a4 and swap the MAF's, clear the code, and drive it for a bit to see if it comes back. if it doesn't you need a new MAF.

 

Alright thanks I'll try to find one......did this have to happen at christmas damnnnnn