bad smell - 92 coup deville

 Hi i'm new to the forum, i have a 92 coup deville with 73,ooo miles ,it runs well when driveing but idels a little rough and as a bad smell (like rotten eggs) what can that be.Thanks Sev



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the smell could be attributed to bad catylitic converter or pcv valve.

Also check for vacuum leaks. Is service soon or now lights on ?  Check for E codes and post.