Dipstick affecting idle and DV solenoid issue

[Austin White]

I have been experiencing an underboost issue , so today i replaced the dv (reg G) with rev D. Yes a down grade, however I didn't know what was on my car.

On a side not, the solenoid on the DV valve was the issue, the seals and gasket looked brand new, however with ODB11 I couldn't make the solenoid fire. So if there is enough people who say rev G is better to have I will replace use the old sealing components and the new solenoid. Anyone had any issues with rev D?

After taking the car for a hard spin to see if could get the fault to re-appear. Luckily it didn't, so for now, rev D will suffice. However, a new code P0506 came up. Looking into idling issues I removed the dipstick when the car was idling (warm) which made the revs increase to a more "normal" level and didn't seam so lumpy.

Looking into it, the PCV seams to be the issue with the dipstick affecting the idle? Does anyone know if I replaced the PCV the issue would go away?

I am also looking to clean the intake valves at some point when I have the time.

FYI my car is a 2.0 TFSI quattro on 107,000 miles

 

[LEE69]

The dipstick as an "o" ring that fails. It's a sealed pcv system so any leaks and it can flag the code

 

[Austin White]

I checked the oring today and it looks fine, but ofcourse that deosnt mean it is sealing properly.

I have also read this post : https://www.audi-sport.net/xf/threads/pcv-is-working-correctly.380810/
Which unfortunately ends without a concluding post to wrap it all up.

I have also watched this video:

The two of them seam to contradict one another. I don't see why removing the dipstick or filler cap would have a negative impact on the idle. By negative I mean lumpy or reduction in rpm.

If the dip stick or filler cap is removed the positive pressure in the crank case will become atmospheric pressure. The engine will have to work less hard to turn over as it isn't pressurising the crankcase. The PCV won't be open and therefore allowing oily dirty air into the intake and so I would have thought that both of these would make the idle better, smoother etc.

I have just checked and removing the filler cap or dipstick makes the idle worse. The filler neck was being sucked back in when I was removing it. Does this means the crankcase should have a vacuum? Therefore negative pressure.

I'm sure it comes across but I'm a little confused. Why is the valve called positive crankcase ventilation when theres a negative pressure?

Or does the pressure build throughout driving and car becoming warm and the PCV maintains a certain pressure, to then not over pressure the crankcase?

Next to the PCV there is a noticeable oil film (please see attached photo), which leads me to suspect the PCV isnt working and so the pressure is finding the path of least resistance out of the crankcase.

Thanks in advance