Past Bronco Owner
Clogged Cat of the month.
Add to the above post. When I changed the plugs after I bought it, the two right rear plugs were OEM originals with 103k miles on them. I think the combo of the two just melted the whole thing. From the back side about 90 percent to the squares were plugged.Fouled plugs can cause unburned fuel to overheat the converter and melt the catalyst to a solid mass. If the O2 Sensor is not functioning properly it will give the ECU incorrect readings of exhaust gasses. The faulty sensor can cause an excessively rich or excessively lean condition. If the mixture is too rich, the catalyst can melt down. If the mixture is too lean, the converter is unable to convert the hydrocarbons into safe elements.