Ok, I need some help here. I think the part that I am planning on replacing is the PCV valve... First of all, I have a '93 4.0. The motor has 2 "valves" on top...one towards the front of the motor that has a tube that runs to the air filter and one towards the back that has a smaller tube. I am having an issue with the rear "valve" It is making a fairly loud sucking sound and the jeep will not run unless I keep giving it gas. Any help as to what part this is, and if it may be the cause of my rough idle would be greatly appreciated!