Light whine underhood?

[ZachMan]

I read about cleaning/replacing the IAC and I am not sure if thats what I need to do or not. I have a 2000 XLS w/ 49k miles on OHV. My idel seems ok, it may be a little high, but it has gotten colder. It starts perfectly, but I have noticed under acceleration I can hear a slight whine and it gets kinda faster the fast I go. As soon as I let off the pedal it goes away. (No I don't have a blower, lol)

I am about to leave work and I will try to pay real close attention so I can pin point exactl when it happens. My serpintine belt is in good condition also.

Does anyone know what might be causing this?

 

[ZachMan]

Ok, its not a whine, more like a rythmic sound. Its just the sound of the engine I guess, but its kinda annoying.

 

[Lexian4x4]

Could be the idler pulley. I had the same issue and my mechanic put his stethiscope on the pulley to determine that the bearing went bad causing the whine.