R32 hard start, vacuum leak, rough idle, and P0174 and P0171


New member
Iowa, United States
MkV R32
Just picked up a used R32 with 123k on the clock and it is having a hard time starting cold and popped the 2 codes in the title while I was driving gently around town. Idle seems rough at all temperatures.
There is also a loud, and I mean REALLY loud hissing or ringing sound coming from the valve cover like in this video
If I cover that hole, the engine gets rougher, if I remove the oil cap, the engine idles rougher but the oil cap is easy to remove. Car seems to have plenty of power and response and no issues when under load. If I hold the throttle to the floor the car starts better and starting fluid will start it up almost immediately with no throttle. There is a slight oil leak from the valve cover as well.

Community fix on Alldata (I have it through my school) is the separator in the valve cover, which I believe is part of the PCV system.

Anybody have a similar experience or have any other thoughts on what the problem may be?