Bad Catalytic Converter
 

Last week, my 1998 Ford Expedition with 163,000 miles started running rough going to work. When I got home I put my OBD on it and it showed 2 fault codes. One code was a bad oxygen sensor, and the other was a misfire on cylinder 6. I had recently replaced all of the coils and plugs so I only replaced the plug in the number 6 position and also replaced the bad oxygen sensor. The Expedition still ran rough. Being frustrated, I took it to my local mechanic. He is claiming, after replacing 2 more oxygen sensors, ($500) that my converters are plugged and wants an additional $2,000. Folks at work are saying if the coverters are plugged, it would be a gradual decrease in performance and not start missing all of a sudden. What do you all think? Could it just be a bad fuel injector on cylinder 6? Maybe a bad coil on 6? I would appreciate your thoughts.

$500 for two O2 sensors is extremely high and overpriced. I would get the exact code (Like p420 for Cat converters bank 1) and determine which converter is bad. Cat Converters dont cost $2000 on these Expeditions.

Thanks for the response. As it turns out, the problem was not with the catalytic converters at all. Problem was a bad coil on the number 6 cylinder. Never considered changing the coil as I had just done so 6 months ago. Guess sometimes you get a bad one. PS. I called my mechanic who diagnosed the problem as bad catalytic converters and told him he had misread his diagnosis. He got all upset and hung up on me. Class act after all the business I have done with him. Or maybe I should say after all the business he has given me. Live and learn.