My wife's 2006 2.5L new beetle convertible started to idle erratic yesterday. The car would almost stall then idle up to 1500rpm then almost stall. It only happened when sitting still at idle. Drive-ability at speed and acceleration felt flat but it was still driving. On the first day there was no engine error code but this morning I managed to pull two.
The codes were
P2279- Intake air leak detected
P0507- Idle speed faster than normal
After some troubleshooting tonight I managed to nail the problem to a ripped diaphram inside a psuedo PCV valve on the front of the valve cover. The part is called the pressure regulator valve for crankshaft housing ventilation. The down side is that I can't seem to buy it separate from buying a complete valve cover. A new valve cover is $136 plus shipping. Check out the rubber piece that's causing all the headaches.
FYI, I could hear this thing leak and could feel air sucking in the little hole in the bottom of the outer cover of the valve. I had the classic air leak symptoms where I couldn't pull the oil cap off with the engine running. When I shut the motor off I could still hear it suck air in for about 5 seconds through the faulty diaphram.
Hope this helps others that might suffer from this problem. The car is just over 3 years old with 62k miles. I can't believe this rubber part might end up costing $150???