A smell of sulfur coming from a car's exhaust pipe is a good sign that there is a problem with the catalytic converter, according to Cars Direct. The smell, similar to rotten eggs, indicates that the sulfur present in gasoline is not being converted to odorless sulfur dioxide.
Two other possible causes of a sulfurous smell are a broken fuel pressure regulator and an engine that is running at too high of a temperature. If the fuel pressure regulator is the problem, it can easily be fixed with the installation of a new fuel filter.
If the smell is due to a problem with the car's converter, the converter itself cannot be repaired and has to be replaced.