2008 Versa with 1.8l, CVT and 82,000 miles. Vehicle made a noise that changed with rpm that seemed to be coming from the drivers side of the engine. The noise went away but returned later. This happened a couple times. Later we experienced problems with lack of acceleration till finally the car just idles and will not accelerate. There are no engine codes and the noise is not present. This occurred over a week's time. Car will be going to the shop. Any ideas of cause?