I have a 2001 SOHC Ford Focus with 101K miles. About 4 weeks ago, the coil started to die (only 3 cylinders were firing). I drove it to work for three days before realizing and fixing the problem ( a total of 250 miles on three cylinders). After I replaced the coil, wires and plugs, I got a CEL with code P0420 - Cat below threshold on bank 1. Something must have gotten fouled by my driving on three cylinders and putting unburned fuel through the exhaust. My question: could I have spoiled the Cat converter, or possibly just a sensor(s)? I failed the emissions portion of my NY State inspection and have 10 days to get the vehicle re-inspected. I'd rather not spend hundreds on a new converter if possible. Thanks for your ideas! Bill

Drive it for a couple of weeks and see if the cat will come back online... that's what I'd do...