I just picked up a 90 YJ with the 2.5 4cyl. It is leaking oil into the air cleaner box through a little hose that I thought ran from the PCV valve. I took the 'valve' out only to find that it is only a vent type thing. No check valve or ball in it at all. I suspect some blow back from a posibble valve problem. Any suggestions before I go and tear the head off of this thing and get a valve job done??