newmoon

I received a letter saying there is a service campaign to replace the PCV diaphragm on 2011-2014 Audis with the 2.0T engine.

You can check for recalls with your VIN here:

Audi Recall Services by Vehicle Identification Number

newmoon

I had this "17F9" service done last week. At first they just replaced the PCV diaphragm with a "20 mbar" part 06H-198-542-A. But then my engine was starting up, idling and accelerating very rough and almost stalling. So I brought it back in and they replaced the whole crankcase pressure regulating valve module. Runs perfect now.

NABS4

Is this related to oil consumption?

newmoon

Not directly. The letter just says that the rubber diaphragm in the crankcase pressure regulating valve may break. Since this is part of an emissions system, it gets monitored by the OBD and the check engine light will illuminate if it fails.

However, I do believe a failed valve may cause excessive oil consumption and even carbon buildup over the long-run. My thinking is that the valve is supposed to stop the intake manifold vacuum from sucking out too much crankcase blow-by gases. But if the valve fails, lots of blow-by gases which may contain oil vapors, will be sucked into the intake manifold. The oil may get burned causing excessive oil consumption, or deposit on the intake valves causing carbon buildup.