Ford had a problem with bad cats on my Contour. It was a '97 and the
cats died around 30 or 40k. The check engine light came on and I took
the car back to the dealer. It was a problem with the cats, either the
design or materials, IIRC.
You might also have bad O2 sensors or another problem. If you have too
much hydrocarbons leaking through, this could cause a problem, too.
You said there was no problem upstream. I would definitely ask if you
haven't already. Also, I would definitely take the truck to autozone or
someplace else where they read the codes on the OBDII for free. I would
also ask the dealer if there are any TSBs on the problem.
I took it to the dealer to have it diagnosed, I already read the codes
myself with my reader, P0420 and P0430. Ford dealer did their
diagnosis and said there were no problems upstream. The technician
said sometimes one misfire will do it, but I'm still skeptical.
The only think I can think of is to test my injectors by pulling the
rail off and charging the fuel pressure so see if I get any drips on
some paper towels.
I'm just not convinced that it wasn't raw fuel that killed my cats.
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