Explorer has loud humming noise
 

I friend has a 2000 explorer with about 50,000 and it makes a loud humming noise. The noise comes and goes. You can feel the noise in the air box and that is where the noise is the loudest. I looked the box over and could not find anything. I thought it was from the little tube coming ou of the front of the box, so I removed it and it did not help. If you lift the lid when it is making the noise it stops. Anyone had a problem like this.

Also the TB looks like it could use a cleaning. The SUV will not stay running with the air tubing and mas off. Should I just clean it like I do the stang? Last time I clean the TB on my grand prix it backfired and the check engine light was on for a day? This is not my vehicle so I do not want to screw it up. Any ideas would help.