My 1997 Pontiac Sunfire has been making a squeeling/whinning sound when idling which worsens when accelerating until at about 40 mph, then lessens. It has been doing this the past few days. Tonight, it started making a knocking sound only intermittenly. The sounds seem to be coming from drivers side rear of the car near the tire. The tires are not low, and I am not having any problems with braking. I know very little about cars - so I am not sure what could be causing this. My car is automatic, I think the engine is 2.2 L.