bad idle but runs good

Jeep is a 1990 4.0 with an aw4.

Well, I am trying to track down a bad idle problem and have found that when I unplug the rear crankcase hose the idle goes to normal but there is sure alot of vacuum coming from that line.
What could cause this and what could be the possible fix? :dunno:

Kim

I have tried taking off some other vacuum lines and some help bring the idle back and some don't. I am not to familiar with the vacuum lines on the 4.0 as I have not yet had a reason to. Any suggestions as to what this could be?

inside the valve cover under where the two hoses connect there are two small chambers that get clogged up with carbon deposits. so pull the valve cover and clean those out and that should fix you up