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Codes P0507 and P0171

Tiny
HSURQUHART85
  • MEMBER
  • 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
  • MECHANIC
  • 30,869 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
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  • 14 POSTS
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
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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
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  • 14 POSTS
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
SATURNTECH9
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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
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  • 9 POSTS
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
SATURNTECH9
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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
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  • 9 POSTS
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
Tiny
SATURNTECH9
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So you have the 2006 A4 quattro?Which engine?
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Sunday, September 30th, 2012 AT 11:00 PM
Tiny
COBRAPHILIP
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  • 9 POSTS
A4 quattro 2.0T.
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Sunday, September 30th, 2012 AT 11:39 PM
Tiny
SATURNTECH9
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There is no iac it uses a throttle servo to adjust idle heres a tip I found for code P0171 let me know what you find.

If you have a B7 (2005.5+) Audi A4 with the 2.0 that has a rough idle and complaint of hesitation along with a lean code and other codes (mine was a misfire, fuel pressure reg code, and idle speed code). Try and take the oil cap off when it is idling. If you cannot or when you do it sucks a rush of air into the engine then you have a PCV issue. These PCV's are crappy and have been revised (so I hear). It is located under the engine cover on the drivers side of the valve cover (see pics). The normal problem is they crap out from the boost pressure and then leak boost into the engine giving you a lower than expected boost pressure. Some times (like this) they can be damaged enough that they give a straight vacuum to the valve cover. Although they shape and design might be vastly different then that of other normal PCV's it is still suppose to perform the same task. There are after market tuning companies that make full metal versions of this unit that retail from 99-150 dollars. The dealership had them for about 60 bucks. Your choice.
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Sunday, September 30th, 2012 AT 11:48 PM
Tiny
COBRAPHILIP
  • MEMBER
  • 9 POSTS
Wow lots of suction in the oil cap. I hope to replace the PVC tomorrow. I'll keep you up to date on what I find. Are the pictures located somewhere else?
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Monday, October 1st, 2012 AT 1:13 AM
Tiny
SATURNTECH9
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Heres the pics let me know how it turns out.
Images (Click to make bigger)
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Monday, October 1st, 2012 AT 1:35 AM
Tiny
HSURQUHART85
  • MEMBER
  • 14 POSTS
Where can the metal aftermarket PVC be purchased from? Do you have a reputable site you trust?
Also, if I went with the dealer, is there a way I can order that part online? Or do I need to call them. I live in a city that does not have an audi dealer.
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Monday, October 1st, 2012 AT 2:02 PM
Tiny
HSURQUHART85
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  • 14 POSTS
Also, how do i know which version of the PCV I have? Im seeing stuff like "n" and "p" versions.
Im currently looking at this website :http://www.urotuning.com/Engine-PCV-System-s/2367.htm

The replacement part looks just like the original. They also have on that comes with a metal "breather tube". Whats the difference b/t all these?
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Monday, October 1st, 2012 AT 2:12 PM
Tiny
SATURNTECH9
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Audi's are far from my specialty let me doing a little research on this.
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Tuesday, October 2nd, 2012 AT 5:36 AM
Tiny
HSURQUHART85
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Okay, greatly appreciated. Do I NEED to replace the breather tube? Or can I just replace the PCV itself? Obviously as little money spent is better.
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Wednesday, October 3rd, 2012 AT 7:04 PM
Tiny
SATURNTECH9
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The pcv valve is leaking vacuum into valve cover so I would just replace the pcv.
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Wednesday, October 3rd, 2012 AT 8:12 PM

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