Hi Everyone,
My 2004 A4 (1.8T FWD) has been idling rough and I got code P0171 which means "running lean". When checking for a vacuum leak, I noticed that the pancake looking valve at the rear of the engine (p/n 06a129101c) is sucking around the top of it at idle. Is this normal? If I plug the "leak" with my finger, the engine stalls. Anyone have any idea at all? Thanks in advance.

 

A little more info ... the valve is item #15 on this .pdf

http://peteandmichelle.lunarpages.co...-2003-2005.pdf

Its called a Pressure Regulating Valve.

 

It must be a hell of a leak to cause the engine to stall and cause a lean code. Generally the PCV valve doesn't cause any fault codes besides burning oil in the intake. If you replace the PCV valve make sure you replace all vacuum check valves while you are in there to keep yourself from further headaches. They kind of look like #25 in your link.
Then tend to crack and cause this condition also.

 

I answered my own question... replaced the Pancake/Puck valve with a new one from the dealer (p/n 06a-129-101-F), cleared the P0171 code, and now it runs like new again! No more codes and no more rough idling either. Awesome!

 

I had the same problem except I was sent part # 06A 129 101 A and the valve i pulled off my car is the 06A 129 101 C.

Can i use the "A" on my car (2004 Audi A4 quarto) or is the actually functionality of the two A vs. C different. Spring rate? vacuum control? etc.

The only mechanical difference i can see is on the port coming out of the bottom, It is slightly smaller in diameter but i can make it fit perfectly with a reducer. Can i use it like this? I started the car and it idled perfect but i am afraid to drive it.

 

So I had same issue with air leak around the valve, replaced it as well as the hose under it, and after clearing the check engine light, I STILL have a rough idle. Any ideas?