Cleaning the pickups and wheels is a start. I'd also look at the connection between the trucks and the frame, I don't know if that car has a wire direct from the trucks for the outside rails. Also, make sure both pickups are connected measure the resistance between the two center track rollers.
Finally, you can consider adding my YLB - RailSounds Battery Replacement (RS-Lite) battery to the car to ride over the power interruptions.