Ok I have a 2005 Audi A4 1.8T and my P0171 error came up couldnt find any problems with houses. I took it to the dealer the charged me 90$ to look at what the problem was they told me that my Mass air flow sensor was bad which i really doubted, i went home and i have cleaned it with MAS cleaning solution, my Check Engine light came back on I bought a new AIR Flow Sensor, 2 days later same light came back on with same code, i got it smoke tested, checked my MAS again it was fine, checked spark plugs, checked fuel injectors they are fine, I really dont know what else to do and everywhere i go they just wanna charge me more and more and im lost. If anyone could help please let me know thanks.

nick

 

Make sure your air filter isn't dirty or constricted. If you already eliminated hoses and MAF, then it is probably your front oxygen sensor (though it seems soon for a 2005). It's an easy DIY since it's quite visible from under the hood. The second sensor is further down on the exhaust but functions as a check. It' sup to you if you want to do that one, too.