Y breather hose & P0171 code?

k95ranger · #1 (**permalink**) 10-26-2009, 11:54 PM

On my 1.8t jetta I have been getting p0171 code. I replaced MAF, fuel filter, front 02 sensor, dipstick tube, secondary air pump tubes, breather tube and "Y" breather hose. I have noticed that the Y breather hose is suctioning itself shut while the engine is running. This was the reason why I replaced it and I thought with its age that it was soft and needed to be replaced. So I replaced it and noticed that it is doing the same thing. You can really hear the pressure regulator valve sucking in. Is this a sign of a vacuum leak somewhere? Why would the breather hose suck itself flat? It idles pretty bad at cold start ups and will even die out when you make your first, second and sometimes third stops. After it warms up it idles like it is going to die but never does, but will drop to 500 and jump back to 700/800. Any ideas of thing to check. I am new to the vw world but I have started to learn from everyone on here of common problems, parts and repairs.

TTTurbo1.8T · #2 (**permalink**) 10-27-2009, 12:46 AM

Have you checked both the upper and lower PCV hoses for tears and holes?

mikesal5 · #3 (**permalink**) 10-27-2009, 08:27 AM

i will bet its your pcv valve stuck, remove it and spray some carb cleaner until you hear it rattle when you shake it, put it back in and youre done

k95ranger · #4 (**permalink**) 10-27-2009, 11:11 AM

I changed the lower breather tube and upper breather hose, so no cracks there. Is the pcv valve the pressure regulator valve which is the hockey puck looking valve? If not where is the pcv valve located? I am new to VW's.

TTTurbo1.8T · #5 (**permalink**) 10-27-2009, 07:13 PM

PCV valve is under the intake manifold

k95ranger · #6 (**permalink**) 10-28-2009, 02:00 AM

i know which one you are talking about. Itts the one piece bleeder valve and it rattles. I also checked the suction jet pump also known as vacuum amplifer and that is good too. Any other suggestions?

TTTurbo1.8T · #7 (**permalink**) 10-28-2009, 07:16 PM

Not sure how you check it but the check valve that connects the PCV ventilation hose to the inlet pipe just before the turbo is that working fine?

k95ranger · #8 (**permalink**) 10-31-2009, 03:52 PM

I found out that the pressure regulator valve was clogged. The small hole that sucks in under the lip had some build up in it. I soaked it in rubbing alcohol and then, no more flat suction y breather and no more P0171. At least for now. I had no other leaks and evrything else is good.

TTTurbo1.8T · #9 (**permalink**) 10-31-2009, 05:32 PM

Yeah that's the valve I was thinking of...good to know...I'm willing to bet this is a common problem with higher mileage cars.

k95ranger · #10 (**permalink**) 10-31-2009, 06:28 PM

After reading all the post from people just ruling these out and how they say that they aren't important, I just thought the same thing. But in my case it wasn't functioning correctly and its easy clean, but when you check them it might act like air is flowing in all directions but It can still be restricted. So it can also be a cause of lean codes. Its that small little hole that can cause the problems. It sucked because I even had vw techs overlook it too. They are suprised now and glad they know.

arthur solalinde · #11 (**permalink**) 08-13-2010, 09:32 AM

Where is the pressure regulator valve located?

AgGTI · #12 (**permalink**) 08-13-2010, 10:03 AM

Quote:

Originally Posted by arthur solalinde

Where is the pressure regulator valve located?

Arthur - from the Y breather hose at the top of the valve cover follow the hose that routes toward the back of the engine. It will terminate at a "hockey puck" looking thing which locates onto the big pipe next to the MAF sensor. It sits next to the diverter valve.
Funny, I read a lot about the PRV yesterday. I was thinking of changing it pre-emptively.

arthur solalinde · #13 (**permalink**) 08-13-2010, 10:52 AM

oops, im sorry, this is for a 01 1.8t passat. is it the same location?
recently i accidentally installed a K&N air filter soon after that i rcvd a system too lean code, i was told K&N was a no no for vw's. could the oil on the filter ruined the MAF sensor?

AgGTI · #14 (**permalink**) 08-13-2010, 10:59 AM

My first thought was the PCV valve. The vent hole in the PRV is pretty small, I'm suprised that it could suck the y-hose flat - I would have thought that maybe some crud is stuck under the diaphragm in the PRV that is not allowing a good seal between the PCV side and the turbo inlet pipe. Anybody know if you can you reach inside the valve to clean the diaphragm?
I just replaced all my breather hoses with silicon ones as the regulars on the forum know. When I pulled the old hose of the PRV there was a lump of dried oil crud sitting in the end of the hose - it was like a small piece of coal about the size of a small pebble about 3/8" diam. This is why I started to read up on what the PRV does.
I'm likely going to replace mine and upgrade the DV to the Audi TT 225 hp one soon.

AgGTI · #15 (**permalink**) 08-13-2010, 11:05 AM

Quote:

Originally Posted by arthur solalinde

oops, im sorry, this is for a 01 1.8t passat. is it the same location?
recently i accidentally installed a K&N air filter soon after that i rcvd a system too lean code, i was told K&N was a no no for vw's. could the oil on the filter ruined the MAF sensor?

I've had a drop in K&N filter for the lifetime of the car - I'm still running the original MAF after 8 1/2 years. The K&N is fine as long as you don't over oil it after you clean it.

I'm not sure about the PRV location in your Passat, sorry. I would try and follow the hose that comes off the Y-breather hose and see where it goes. It should end up in the hockey puck PRV on top of the Turbo inlet pipe right after the MAF sensor. Don't know if VW had a different arrangement in 01. Somebody else might chip in. Also, don't confuse it with the diverter valve (DV) which is a similar shape but has a small vacuum hose connected to the top of it.

Your too lean code might be more related somehow to your breather hoses being sucked flat.