Oldsmobile/Buick Repair: Troubleshooting, rotten egg smell, speedometer

Question
I have a 1992 Oldsmobile CutlassCiera SL,6 cyl.,3.3L.Twice in the last week I was driving at 55 mph when my speedometer suddenly stopped working and the engine seemed it was going to quit.It began to"miss".Also I noticed it had sort of a rotten egg smell.Then all of a sudden the speedometer began working again ,no smell and the car ran good.Can you please tell me what happened and the cause of the trouble.I appreciate your help and Thanks!

Answer
hello elizabeth
this is what u are smelling is a bad catlaic contverter it will havt be replaced and the compuiter will have to be reset . and u will be fine any good excaust shop will chabge it for u . good luck to u hun and u have a very pretty name pete