Located at the back of the engine compartment on the passenger side. The single white tube that comes from it is dry-rotted. There is a lever on the valve that does move and air feels to be getting pushed out.

https://www.f150online.com/forums/me...ngers-side.jpg

https://www.f150online.com/forums/me...ubber-tube.jpg

https://www.f150online.com/forums/me...eplacement.jpg

Any clue as to what it is and how I can repair this tube? It leads to a wrapped bunch of wires and does not look like something fun to mess with. Could this be the cause of my rough idle and flashing 'service engine soon' light?

 

I believe that is the blend door actuator and its vacuum control line. The broken hose results in a vacuum leak. Remove the the portion of the hose that is in disrepair. Get a piece of new black vacuum hose that will fill tightly over the white colored hose and replace it with that. Use a bit of rtv if you want to make double sure it seals.

 

Bingo! ^^

 

Na its the flux capacity, u add blinker fluid to it...

for real tho, 5rangers got it. when this sees a vacuum loss it defaults to defrost only.

 

Actually, thats the outside blend door vacuum line, when the system is on Max A\C or Off then it receives vacuum. When the system was on either of those settings he would have a vacuum leak, but other than that he probably didn't notice much of a difference.