# P2279 and P0171 with Rough Idle on Initial Start



## Distortlife (Sep 27, 2013)

Here's my story...

My Jetta used to make a somewhat loud noise, kind of hard to describe, for a few seconds when it was first started as the RPMs rose just a little high and then leveled out. That used to be normal.

Then, the check engine light came on for my wife on her way home and it developed a very erratic idle and I could hear a whistling sound every few seconds. Researching on this forum I decided it was likely the PCV Diaphragm. I popped it off and low and behold there was a large rip in it.

I ordered the Dorman PCV Diaphragm replacement and installed it.

Now, it no longer makes the loud noise it used to on start up. In fact, the RPMs don't rise at all, they fluctuate. It's a bit of a rough idle for like 5-10 seconds then it levels out and seems fine. However, after driving for a while the check engine light inevitably comes on and I get P2279 and P0171.

I read a post that someone used this same replacement part and it took a few days for it to "seat" itself, but I've driven it for a week and it's the same. I'm wondering if my part is faulty or perhaps I have another issue.

Anybody seen this before? Any ideas? I have access to a Vag-Com if someone can tell me what info to pull.

Thanks.


----------



## le0n (Jun 12, 2013)

try to remove your oil cap when the engine is idling. if it is easy to remove, your newly repaired pcv is most likely working properly.

also, your n80 valve has probably failed, resulting in a vacuum leak (un-metered air). 

slide back the passenger side hose clamp, disconnect the vapor line and put your finger tips over the holes (vapor line and n80 nipple) while the engine is idling to see if your idle improves.


----------



## Distortlife (Sep 27, 2013)

The oil cap is still very difficult to remove with the engine running. I'll check the n80 as soon as it stops raining here. I read somewhere that there are two valves for the crankcase breather system. One is the diaphragm I already replaced and the other is the oil filter housing breather valve. Could it be this valve in the oil filter housing?

I'm thinking maybe the new diaphragm I got was defective. The company I bought it from immediately refunded me after I contacted them.


How do I put a picture in my post?


----------



## Distortlife (Sep 27, 2013)

I bit the bullet and paid the $220 for the oem valve cover gasket with built in pcv diaphragm. I could feel a little slop in the dorman housing and when I pushed it tight the idle straightened out so I convinced myself that was still the culprit. The new valve cover seems to have done the trick. It was also quite easy to install.


----------

