Hissing noise, poor idle, stall

[77bronco]

I turned on my 97 5.0 yesterday and thought I was not going to make it home. There is a hissing noise coming from the driver side engine bank. Seems near the exhaust manifold but it is hard to locate.

Seems like a vacuum leak but I can't locate it. Are there any vacuum lines near there?

No check engine light, extremely rough idle, loud hissing (audible from inside the truck with window closed), and it eventually stalls from idle.

Help please!!!

 

[newbi]

Sure sounds like a vacumn leak, I found a broken EGR vacumn actuated solinoid valve in the area where your sound is coming from. Trace all vacumn lines from tree when engine is cold.

 

[77bronco]

I can't find the tree. I tried to follow the line from the brake booster, it disappears behind the engine, seems to connect to the intake at the back.

Remember it is a 5.0 liter if that makes a difference.

any ideas how to find the tree easier? is it on the drivers side?

 

[newbi]

You are correct, it is on the back of the engine, vacumn comes off the intake manifold.