PCV valve humming noise on 2001 Ford Expedition w/5.4

For the life of me, I cant figure out why the pcv valve on my ford expedition is making a humming noise. Pull the pvc out and plug it with my finger and the sounds gone. Put it back in and it starts buzzing like a banshee! Any ideas will be appreaciated before I take it to the dealer and get anally raped.