Just moved into a new house and inherited a dishwasher. The house is three years old and the dishwasher looks about the same vintage. The dishwasher works, but quite poorly. Alot of the plates have been cleaned but still have food residue on them. We are not overloading the dishwasher. I assume the volume of water passing over the dishes is inadequate or the speed of the spray is inadequate. I don't want to throw out an otherwise good dishwasher. Any advice?