What are some causes of a plugged catalytic converter? What symptoms would be present if a converter was plugged?

Your catalytic converter is a vital part of your car's emissions control system. It is rare for a catalytic converter to fail because they are designed to last for the life of the vehicle. However, your catalytic converter sometimes clogs, usually due to a problem in another part of your fuel system. For instance, if your fuel mixture is too rich, your catalytic convert can overheat and even start to melt. If your fuel becomes contaminated or your exhaust system fails to perform correctly, you may also see symptoms indicating that your catalytic converter is clogged.