Crankshaft problem

[tawfiq]

Hi, I am driving a 328 E36 1997.My car stalls when I brake at traffic light or stiop to pay toll. At high speed the RPM fluctuates and the car speeds up and slows intermittently. The starting of the car is also not smooth.The problem started after I changed the piston valves as the engine oil was also getting in the engine.Now my mechanic is saying it is due to crankshaft sensor problem.I have asked him to change it as I dont want the engine to die on me in the middle of the road.What do you think is it really die to the crankshaft sensor? Thanks