I have a B4 Audi A4 Quattro. I have a CEL that is giving the codes P0507 and P0171. I have done a little googling on this but haven't found much help. The only thing that seems to be the solution is replacing the PCV (pressure control valve). Symptoms of the car is that at stoplights or when I'm stopped anywhere with the car in neutral and the a/c off, the engine revs up on its own to about 1200-1500 rpm and then drops. It does this cycle repeatedly. When the rpm drops, sometimes it goes so low that it seams like the engine is gonna stall. Also, this does not happen when the a/c is on. Help!
Tuesday, September 18th, 2012 AT 12:14 PM