Can anyone help with the codes P0507 and P0171?

Tiny
HSURQUHART85
  • 2006 AUDI A4
  • 105,000 MILES

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!

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Tuesday, September 18th, 2012 AT 12:14 PM

38 Replies

Tiny
SATURNTECH9
  • EXPERT
  • 30,270 POSTS

With the codes you have the first thing I would do is check for a vacuum leak.

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Tuesday, September 18th, 2012 AT 12:22 PM
Tiny
HSURQUHART85
  • MEMBER

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!

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Tuesday, September 18th, 2012 AT 12:52 PM
Tiny
SATURNTECH9
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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.

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Tuesday, September 18th, 2012 AT 2:31 PM
Tiny
HSURQUHART85
  • MEMBER

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?

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Tuesday, September 18th, 2012 AT 5:21 PM
Tiny
SATURNTECH9
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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.

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Tuesday, September 18th, 2012 AT 5:37 PM
Tiny
HSURQUHART85
  • MEMBER

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?

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Wednesday, September 19th, 2012 AT 7:11 PM
Tiny
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Any vacuum hoses vacuum sources like intake gasket etc. You made need to remove a engine cover if its in. The way.

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Wednesday, September 19th, 2012 AT 9:13 PM
Tiny
COBRAPHILIP
  • MEMBER

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.

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Sunday, September 30th, 2012 AT 8:15 PM
Tiny
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A iac isnt going to cause the code P0171 you can try smoke testing it.

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Sunday, September 30th, 2012 AT 9:56 PM
Tiny
COBRAPHILIP
  • MEMBER

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.

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Sunday, September 30th, 2012 AT 10:48 PM

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