A few months ago I bought a used 07 5.4 4wd with 114000 on it. I have since replaced the plugs because it was bucking at low rpms while under a load (I have no clue how I did not get the truck to do this on my 3 30 minute test drives). I did this within the first 200 miles of owning the truck. That problem went away. While doing my plugs I replaced the fuel filter also. When I did the plugs a little bit of penetrating oil got into the cylinders, I blew as much out as I could, I got some white smoke after I started it up when I finished. A week later the CEL popped on, P0430. I reset it hoping that the penetrating oil just gummed up the sensors or something, light came back on so I switched the downstream O2 sensors to the opposite side to see if it would switch to a bank 1 code. Still getting the same code. I also watched the O2's on my scanner, the bank 2 downstream is fluctuating more than the bank 1. I realize that I need a new cat but I live in the great state of California, I cannot seem to find an aftermarket cat for my truck. I heard that aftermarket ones fail quickly though. But would that little bit of penetrating oil kill a cat? Also it idles a bit rough at a stop light, would some fuel system treatment help the rough idle? I am just trying to make sure that there is no other issue that might kill a new cat. Any help would be greatly appreciated.
-Ryan

 

If your cat is dead.. it was not the penetrating oil that did it , it was more likely the Bucking under load for 14000 miles ...plugs should of been changed at 100K