When I start my 01 ram with 5.9 I hear a Hiss. It sounds like a pin hole in an air hose. It doesn't do it a WOT but no matter what speed as soon as I touch the gas I hear it. I let off the gas and I still hear it but it fades out. Any Ideas?

 

OK, you need to be a little more specific. On the surface it sounds like it might be vacuum related. Lets see. Do you hear the hiss inside the cab? Are the windows open or closed? Did you try raising the hood and get a general location of the sound.
You see, you are hearing a noise/sound; we can't and are not there. Could it be a HVAC vacuum hose under the dash? No? Outside under the hood? Left or right side. If you are under the hood and hit the throttle, where/what does it sound like.
I'm sure anyone here would be more than willing to help but we need more input!

 

I am sorry for being so vague. Windows up or down. Pretty loud. Seemed to be comming from under the hood on the driverside near the back. Someone mentioned the gasket under the breather box ontop of the throttle body.I pulled the breather box on top of the throttle body. I seen my gasket was broken. Got a new gasket for the breather box and put it on and it seems that the hiss got quiter and more intermentant. Now after I tried the gasket and I still heard it Pulled the breather box back off and the sound appears from the throttle body. The square port behind the butterfly valves. What is that port for?

 

GOT IT!
That's the IAC (idle air control). Take the time to do this right. Remove the throttle body. Do an OFF engine cleaning so as not to be gunking up the intake, plugs, etc. While the TB is off, remove the 3 sensors; IAC, TPS, and MAP. Once you remove the IAC, you should see your problem. CRUD! Seriously, though, what you are hearing is the air trying to get by the IAC port and all the garbage on it, so it's whistling by the port making the noise. Use a toothbrush and Brake parts cleaner. You'll need a new TB gasket, about $2.
Also, make sure (I'm assuming you have the factory filter box) you get the filter box seated properly when you put it back together. Sometimes they can be a booger.
WC

 

Thanks Wayne.

 

That sounds like a problem i have right now. just another thing to add to the "to-do-list"