Hissing sound when running

My car(90' olds eighty eight royale) is making a hissing sound when the engine is turned on. It sounds like it is coming from the general area of the back spark plugs. When i turn the engine off it hisses and then dies down within about 2 seconds. We just replaced the spark plugs but my grandpaw kinda laid on the engine while puttinb the pesky back plugs in. Dont you think that if it was a spark plug the engine would knock hard?? That what my mom says but i still think it could be a plug that was forgotten to be tightened.

I donno what do you think??

It sounds like you broke a vacuum line on or near the fire wall or the rear portion of the engine.

What would cause that. We didn't touch that area. hmmm

Sometimes because there dry it doesn't take much to crack them,if you listen closely you will find it,good luck.

I still cant find it anywhere. Too many hoses and wires are there to single it out.. Im not sure what to do.. Hmm

I can hear it coming from the general direction of the steering thingy lolz.

spray soapy water on and around the vacum lines
that will cause the one with a leak to bubble

thx i think i found it.

So ,whatcha find?

hose was loose