I drive a 1996 Camry XLE V6 and my engine has been humming loudly and vibrating my dash during idle and low speeds. This has been going on for almost a year. About 3 years ago, I had problems with my idle control valve where my engine wouldn't stay idle when started from a cold start. I replaced the idle control valve and the problem went away immediately.

I'm guessing the problem right now may be related my problem before or to the air compressor. Does anybody else know what might be going on?

 

could be a vacuum leak. i'd check all the hoses while the engine is running. i'd particularly check the pcv hose.