EDIT: just thinking this over in the back of my head, it could be stuck - yes. but it could be stuck OPEN, which would cause a vaccum leak and create a lean misfire. to check this, take the hose off at the PCV valve, and block the PCV valve with your thumb. all in all, pretty quick checks!
and if you just want to service it for peace of mind, grab some throttle body cleaner (carby cleaner) and remove the PCV. soak it in a cap full of the stuff. shake it round a bit and it should start moving freely again. do your throttle body while you're at it.
thats basically what the mechanic has said but he told me to just buy a new 1 cause it should be pretty cheap and throttle body and injectors have already been cleaned