happened to me a year ago when the temp. was at about 98 degrees outside.... pretty hot day... the air box was vibrating pretty good.. that was the noise that sounded like a moose.. when i got home i opened the air box and made sure it was tight down and then put in a new air filter... i never happened again..... dont know if this cured it or not.. the next step would be to check the idle air control valve....
