i have a 2008 explorer eddie bauer 4.0. a/c blows fine up until i accelerate then system stops blowing. each time i accelerate there's a hissing noise coming from the passenger side. what is this.

Sounds like you have a leak in the A.C evaporator. There is something you can try with no promises that it will work but try adding some freon stop to A.C system worked for me when I had a leak in my vehicles evaporator. You can purchase at part stores like autozone. If does not work you are going to have to replace evaporator.

thanks !! i heard it might be a vacuum problem too. hopfully someone else chime in with another suggestion. an evaporator sounds expensive

After thinking about it the blend door maybe vaccuam operated. This door is what opens and closes between the A.C evaporator and heater core depending on what setting you have it on. So look underneath passenger side dash you may have to remove a few screws to see blend door connections.

Ok i think i got it. underneath the glove box toward the left there's a row of vacuum lines blue,pink,black,grey,white. they were all plugged in but i guess not enough. after i checked them all drove to work and back no hissing no ac loss at acceleration. i think im going to tape these hoses make sure they stay in place. im assuming maybe the floor mat pushed up to far up and caused it. but anyway thanks guys for your input.