It doesnt matter if im in park, neutral, reverse, or drive, I hear a weird sound at idle. Its like a timed snake hissing, it will pause for a moment, then begin-grow in volume-die down in volume- and stop within a second, and its keeps doing it, its kinda audible, i dont know what it is or where its coming from, underneath somewhere

 

sounds like a little exhaust leak. Take it to the dealer and have them check it out.

 

Hopefully, it's not a loose spark plug. Get it to thy dealer and let a tech hear it.

Dan

 

I bet it's your IAC (idle control motor), Ford with bad IAC makes a hissing noise on idle. Try to unplug it, the engine is going to die when you do that, but listen if the noise goes away right when you unplug it just before the engine dies. If it dos you have a bad IAC.

Swede///

 

I had a sound like that a few months ago, it hissed like pressure escaping. Ford replaced my IC and it went away.

 

Your inter- cooler?

Dan