google says rotten egg smell is from too rich a fuel mixture running thru the catalytic converter.
the rotten egg smell is hydrogen sulfide/disulfide I think. I don't think fuel has much sulfur in it, wouldn't say it's considerable, but you probably need very little sulfur to form enough H2SOx to smell it. Engine operating temp being too cold combined with rich fuel mixture passing uncombusted fuel and not enough oxygen to a not hot enough cat is probably the mechanism for the rotten egg smell. It seems like this smell is not a symptom of a clogged or plugged cat. If the cat were plugged, there is a very noticable performance and economy drop, like not being able to get over 2k or 3k rpms because of exhaust backpressure.
[ November 14, 2005, 02:22 PM: Message edited by: 1 FMF ]