Its a vaccum check valve, it would be no small vaccum leak if that fitting was broken off though. The engine management ona 2.7T is extremely sensitive to leaks.
I wouldn't by pass it if i were you, its about a $40 part at the dealer, they are usually in stock.

 

sorry should have elaborated a little more on my reply, what i meant by by pass was for test purposes only, not to make the repair permanent, the valve does need replacing regardless. and yes a very small leak will cause all sorts of problems and i should know i do this for a living. regards Vinny, ps let us know how you get on, i am confident of the outcome.

 

Alright, I picked up that vacuum check valve today. Car started fine however the CEL still came on. It has a rough idle but thats just about it. The car drives perfectly fine and normal and as soon as I start moving the CEL goes out. If I let the car idle for more then minute the CEL goes back on however the rough idle never goes away. Any thoughts?

 

You probably still have a miss-fire, either you still have a small vaccum leak or the spark plugs are fouled up. Mine has a slight random miss-fire in my S4 at idle because my plugs are fouled up. But mine doesn't shake, so i would say its still a vaccum related problem.

 

I would have to agree. I just pulled the plugs and they look fine. Back to finding this damn vacuum leak!!!

 

Ok, I give up. I spent all day Saturday and now all tonight trying to figure out what this things problem is. I cant pin point it to save my life. I keep getting the same P0300 code even after driving it for a few miles. It drives fine but still idles terrible. I can hear a high pitched hissing telling me theres a vacuum leak but I cant find it without the proper tools. I guess ill be heading to a place I haven't been in 10 years... The local auto mech. I've rebuilt entire engines in my day and can tackle just about anything but this one has me stumped. Sorry for venting but this has me pissed!!![sm=headbang.gif]

 

Well before you go taking off to the mechanic i have one other place you can check. You have to take off the turbo Y pipe to get to it, there is a little white vaccum T fitting that commonly breaks off that i usually find when i smoke test the intake. You can try and take apart the motor to see if you can find it, or you can take it to the mechanic and have him smoke test it to find the leak.

 

Interesting. Its not the bigger one I just replaced is it? I can't recall seeing any white T fittings but I can certainly give that a look. Theres a whole swarm of large vacuum lines on the rear side of the engine that are not very easy to get to, that not where your talking about is it? Any specific location????

 

I took the liberty of taking a quick pic.

[IMG]local://upfiles/47422/B490189354424FB69B49A3F0CE9CA211.jpg[/IMG]

 

Its wayyyyyy deep behind the motor, and it isn't that big.