2008 A4 2.0 Turbo, and on second PCV valve failing. Whistle became evident again after 300 miles and vacuum holding oil fill cap on real tight. Considered blanking plate kit, ordering another valve... but would like the car
tomorrow. Popped off the hose from the PCV valve to the intake and surveyed the situation. Go to thinking it has rather large ID compared to many other PCV valve aplications, esp older V8 north american.
Well lets just restrict the flow a bit & see if system is happier. A plastic plug about an inch long with a 3/16 inch hole through the center fit into the pcv end of the hose securely. Very securely so it cannot exit into intake for sure.
Fired up car after clearing codes (P0171 I think).
Oil cap which was extremely hard to remove, now comes off nicely with just a bit of crankcase vacuum present at idle. All systems happy & no whistle.
Other than periodically making sure smaller diameter hole is clear, can anyone see a flaw in this fix. I'm guessing PCV valve diaphram & check valve were just being disorted by massive vacuum shock & letting to much vacuum
go into crankcase.
Cheers
TheCounty