Urgant!!! Where does this vacuum line go?

[ookageoo]

hi guys im from australia but im hoping you can help me , i bought a 1996 ford explorer with the 4.0 v6 engine in it its an automatic and the idle is fluctuating from 1200 down to 500 the back to 1200 then back to 500 and so on and it also stalls when you put it into gear.
ive narrowed it down to this mystery vacuum line not being connected to anything.
when i put my finger over the end i can feel it sucking in.

ive attached a pic of said vacuum line , i traced it back and it seems to start on the left hand side of the intake manifold the line is red and it has a little connector piece just where my hand is and then after the connector piece the line is black.

thanks in advance for your help.

you can see in the pic it runs back under the front of the manifold and over to the rear of the left hand side of the manifold

 

[ookageoo]

Ill explain a bit better , on the left side (your drivers side ) of the intake manifold at the rear there is a plug on the side that has 3 vacuum lines coming out of it and the line pictured that isnt connected to anything is one of them.

 

[R1dd1cK]

Okay try this. Start the truck. Turn the heat on. Check to see if the heat only comes out of the defrost. Change the heater control to floor vents only. If the heat still only comes out of the defrost then that is the vacuum line for the heater controls. If it does change where the vent is blowing then it is something else. But this will give you a starting point.