I am new to this board and I am hoping someone can shed some light on a problem my father is having with his car. He recently bought a 1995 525i with about 130,000 miles on it. Minus a thermostat and some lights the car is in perfect shape. It only has one problem, when traveling right about 50mph (and so far only when going uphill) the tachometer starts surging back and forth about 500rpm. This is our first BMW and we are not quite sure what is causing this. My father thought it might be the oxygen sensor so he had it looked at and the mechanic found it to be malfunctioning. Yet after replacing it the problem remains?
Any thoughts would be appreciated