Kevin Sneed

I have a 2000 Maxima that's got me scratching my head. I've been having problems with the idle looping and dropping so low that you have to keep your foot on the pedal to keep it running. I've replaced the IACV, cleaned the throttle body, checked for vac leaks and checked the ECU. The problem is, this doesn't happen all the time. Sometimes it will run normally for a little bit (1/2 hour to an hour) then go right back to looping or stalling. I've noticed when it starts struggling, I can hear a motorized whining on and off from the engine area. Any ideas where I can look?