So i am new to this forum but definitely not new to VAG. I found this forum while searching for some answers to my vacuum problems. Saw some really good write ups. So here is the issue....
About 2 weeks it started throwing codes ( po171, 507, and random misfires ). I made some calls to some local friends/ mechanics and started trouble shooting. First was a bad check valve by the air box, replaced it. Then after spraying starter fluid around looking for leaks i found the 90 degree elbow right out of the crank case breather was beyond shot, replaced it. Then i started hearing hissing from the PCV valve located right off the valve cover ( aka pancake valve ), replaced it. I'm still hearng the hissing from back there but can't find it. Yesterday i took out the entire vacuum system. Everything under the intake manifold all the way up to the valve cover. I checked every single check valve, the all looked good and when i blew through them they worked as the should. I looked over every line, they all looked good. I removed the crankcase breather from the block to check for any blockage, everything there looked great. Put everything back together, cleared the codes, took it for a spin. Codes came back again.
Ive read alot about bad MAF and vacuum leaks for these codes. I have cleaned the MAF. I dont believe its a MAF.... and here is why. Every time i give it any kind of decent throttle is will blow the dipstick out and spray oil every where!
The only questionable part i found yesterday was the suction jet or vacuum pump. Here is what i was told on another forum about this pump. Blow through the rear two ports, you should be able too, try to blow through the front port , and you shouldnt be able too. Is there true to this? The reason i ask is because when i tried this and blew through the front port i was able to blow through but it only came out the smaller of the two rear ports.

Any help with would be appreciated, TIA!

 

I'm in the exact same boat. Haven't found a vac leak yet but am still throwing the lean code. I only got the 0171 code though.

Is the car running normally? Ours doesn't run like it has a vacuum leak so I am thinking it's a fuel supply issue. It just got a new fuel filter and with it of course the pressure regulator so now I am thinking it might just be the fuel pump getting ready to give up the ghost at 135K it wouldn't be shock.

Good luck and let me know if you find anything new to solve it.

 

Today i put a new suction pump on, nothing changed. It runs good, has a rough idle though. If i let it get any boost it blows the dipstick out and spews oil everywhere. After i put the suction pump on we got ahold of a smoke tester and checked it out. Smoke testing showed NOTHING, we checked it from serveral different areas with no leaks found. Ordered a fuel filter today but i'm going away so i wont be able to touch it till monday.... i'll let you know
Good luck with yours and let me know if the pump fixes it. i know if the filter doesnt do it thats my next stop too.

 

I cleared the code last night after doing some testing with the MAF and I found that the MAF plug must be a little worn. I unplugged the MAF while the car was running and there was no change which according to most sources indicates it is bad. I pressed the plug down hard when I reconnected the MAF and as of yet the code has not returned.

I am about to take the car out and give it some full throttle boost and run it around at highway speeds and we'll see. It did a few miles today city driving with my wife but she didn't push it at all.

 

The code came back after a day and a half so I went ahead and replaced the MAF. New one went in and I cleared the code. After a few minutes I reconnected the battery and took it out for a good shake down drive.
I ran it at highway speed, ran it at full boost, and did some stop and go city stuff. So far the light has still not come back and everything is looking promising but we'll see.
I went ahead and ordered a crank position sensor too since I got some long crank time starts with the EPC light coming on.
I didn't realize the car was down on power but with the new MAF sensor it seems that it's back in full running happy and healthy.

 

300 miles in on the new MAF and still no return for the CEL. I think this one is solved for our car, hope this helps for you OP.

 

on the smoker did you put in the hose after the MAF ?

did you check the brake hose near the intake manifold ?

you can delete vacuum hoses as well....

check coil packs / MAF

 

long arm.... good deal, glad it worked out

NorthD... yes we put in after the MAF, by the intake manifold and every which way we could. Seriously debating deleting all of it but wasn't sure how that would work on the factory ECU ( its stock, no chip yet ). And as far as the coil packs go... they only have 5k on the coil packs and plugs. All bought straight from dealer

 

Finally fixed it today!!! After 4 hours of vag-coming the hell playing with a couple things and doing some more research i got no where.... then i found a very useful thread on AudiZine, guy had every problem and tried every fix i did. Finally he ended up replacing the pcv under the manifold. So i figured what the hell, i thought it looked good when i had it out the first time but apparently i was wrong. Put a new one in this morning and its running like a champ again!!!

 

great news happy forth