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!
With the codes you have the first thing I would do is check for a vacuum leak.
September, 18, 2012 AT 12:52 PM
How hard is it to check for a vacuum leak? I am trying to do this repair by myself if at all possible as you can tell. What do I need to do to check for a vacuum leak? Thanks for you fast reply by the way!
September, 18, 2012 AT 2:31 PM
You let the engine idle then. Spray some carb spray around all. The vacuum lines intake etc. If the rpms go up down or the engine stumbles and dies. You found a leak.
September, 18, 2012 AT 5:21 PM
Okay, and let say that there is a leak. How do I detetermine where the leak is and what it is I need to replace?
September, 18, 2012 AT 5:37 PM
Use the straw on the carb spray to narrow the stream you can pinpoint it pretty close like that like see if you find a leak and where it is and we will go from. There.
September, 19, 2012 AT 7:11 PM
Do I need to disconnect anything in order to spray the carb cleaner into the engine? What exact parts do I need to be looking at?
September, 19, 2012 AT 9:13 PM
Any vacuum hoses vacuum sources like intake gasket etc. You made need to remove a engine cover if its in. The way.
September, 30, 2012 AT 8:15 PM
Did you ever find a Leak? I have the same codes, same car with 116000. I looked and sprayed the hoses with no luck. Is there a IAC on the car? Any help would be great.
September, 30, 2012 AT 9:56 PM
A iac isnt going to cause the code P0171 you can try smoke testing it.
September, 30, 2012 AT 10:48 PM
A PO171 is a lean code right? It was set 4 times. I thought if it was getting too much air around the IAC would send a lean code. I also thought they said PO507 was a IAC but the parts place couldn't pull one up. I've looked and pulled the throttle body thinking it was attached to it. Didn't see it.