New catalytic converters may smell of rotten eggs when first installed; this is normal and should dissipate after some hours or days of driving. Contents hide 1 Sulfur Smell 2 Gasoline Smell 3 New Converter Smell 4 Old Converter Smell Sulfur dioxide emissions come from hydrogen sulfide gas which, when converted by a functioning catalytic converter, should dissipate into innocuous … Continue reading Why Does My Catalytic Converter Have a Bad Smell?