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Check Engine P0420 P0430 poor mileage and exhaust smell


New Member
May 27, 2006
Reaction score
City, State
orange tx
Year, Model & Trim Level
'97 explorer v6 sohc
So I have a 97 explorer eddie bauer with 4.0L SOHC V6 with 217k miles.

I had a CEL a year or two ago, and I replaced the spark plugs since they were old and needed to be replaced anyway. The CEL went away for a while and then came back. Mileage has slowly gotten worse, from about 20mpg to 15mpg today. And someone told me recently that my exhaust smells a bit like unburnt fuel.. but other than that it runs smooth and idles smooth.

I haven't really done anything about the check engine light until now. I finally got the codes identified as P0420 and P0430 -- catalyst efficiency banks 1 and 2. This means my catalytic converters are plugged, right? If it were just the O2 sensors, then would I still see the other symptoms? What else should I check before I start messing around with the cats?

Would appreciate any advice.