Hello I got a 98 Expedition 5.4L xlt. I need help finding out where a hose connects up to. It's like right under the throttle and by the air intake on the passenger side.

 

That looks like a heated PCV fitting. The center port is for the vacuum line from the intake to the PCV valve. The other 2 ports are for a 1/4" engine coolant line to provide heat to the fitting. One of the lines will go to a supply port near the heater supply port on the front of the intake manifold. The other is a return line that probably goes to the rear of the engine. I can't see where it goes on the back of our 5.4L or 6.8L, either. I can feel the fitting, but can't tell if it's in the head, block or intake.

 

How important is it to have the hose on it or can I put something over it to keep it from leaking

 

I think the purpose of heating the PCV line is to keep any moisture in the PCV valve from freezing and causing the valve to stick. If stuck in a closed position, the valve could allow crankcase pressure and blow-by to damage gaskets and seals. This may only be an issue in extreme cold climates. I guess that makes sense for the PCV valve heater, but the heater on the other end of the hose at the intake seems to be a reach. The PCV valve is a variable flow control valve (using a spring) and a back flow preventer that are sized to match a particular engine.
PCV valves have been around since the '60s and the heaters started to be used in the late '90s. You can cap off the fitting at the PCV valve or go back to the port on the intake to stop the flow. Also, the return port on the back of the engine would need to be capped, but maybe it already is.

 

No the hose was on before I took it to a backyard mechanic that screwed me over and mess up my car. I had drove it up from Arizona to South Dakota last May and I didn't lose a drop of coolant until I took it to him. He also broke a T heater hose fitting that I had to replace as well.