A Catalytic Converter "Efficiency" code should NOT cause any driveability issues UNLESS the "Material" INSIDE the converter is loose and moving around.
When loose, the material can block the flow of the exhaust and that causes lack of power (the engine can not breathe correctly).
A bad coil will cause the engine to run rough (misfire) which leads to Catalytic Converter meltdown. Due to raw fuel entering the converter and overheating it.
Saturday, July 26th, 2014 AT 2:45 PM