Guyz I have a 97 maxima gle and it has about 180k on it. Everytime the car is idle i hear this loud humming noise, and when i look at the rpm gauge sometimes it goes up and down while i'm idle. It only goes up to 1 - 1.5 not, feels like it's revving the engine it self.

Car is driving a little rough, i don't know what the problem is. I change the oil every 3000 miles, changed the transmission oil, do a regular tune up.

About the humming noise, the noise varies when I turn the steering left and right (this is still when i'm idle). I checked the steering pump everything looks good there, i popped the hood open and it sounds like it's coming from the manifold, but not exactly sure.

Please help