I have recently brought a X5 3.0i and I noticed a vlave cover leak and a extreme oil built up on the valve cover and on the engine. I cleaned the valve cover and tired clean the the internal engine. I replaced the cover and after replacing the cover the car started but after driving several miles the car stop 10miles from my house while I was driving. The car is turn over but it is not getting any fire. What would cause this problem? Thanks for the help. 1. Can the O2 sensor cause this problem