Whilst you were not firing one cylinder lots of unburnt fuel will have got
into the cat and 'polluted' it.

Now that all six are firing again, my guess is that a couple of long runs
will warm the cat up, provide exhaust with low levels of hydrocarbon and
allow catalytic conversion of hydrocarbons in the cat' restoring it to
health.


"Jeff Strickland" > wrote in message
...
> The car runs good, no problems. Spark plugs are old, 150,000 miles and 16
> years (1997 vehicle).
>
> I decide to change the plugs. No troubles BEFORE I begin.
>
> When I am done, the engine runs poorly, severe -- or at least notable --
> misfire. I drive for a day or two -- probably about 50 miles or less --
> until the check engine light comes on. I pull codes, a single cylinder
> misfire. No big deal, I discover the plug wire not seated well on the
> plug, easy to cure.
>
> Engine instantly runs better -- misfire is gone.
>
> Now I am driving around with the scan tool connected just to be sure that
> the things I feel in the seat of my pants don't turn into a fresh round of
> engine codes. I don't feel much, and no misfire reports. Life is good.
>
> Hold your horses, life is not so good.
>
> I have a Pending Code, P0430 CATALYST BELOW EFFICIENCY BANK2. The check
> engine light has not come on yet, but if the problem is true, then it
> should come on in a few more drive cycles.
>
> My question is, if I have a misfire will the resulting raw fuel damage the
> CAT or the post-CAT sensor? I was not aware that a misfire could take a
> CAT out. The misfire that I had is in Bank2, so there is a correlation
> between the misfire and the new code.
>
> Of course, there is a strong possibility that the plugs I installed are
> not the right ones -- just because the parts guy says that the catalog
> calls for them does not mean they are right. After putting the plugs in, I
> went to the dealership to get the factory plugs and plug wires -- $230 for
> plugs and wires from the dealership, ouch! -- but have not installed them
> because the engine now feels just like it did before I started working on
> it. (Curing the misfire code fixed the poor operation, entirely, so I'm in
> no hurry to open the hood again. It was very difficult to reach the plugs,
> and if the engine runs then I don't want to do the job over again.)
>
> So, my question is if I damaged my CAT or if it is merely a coincidence
> that I have a P0430 Code in pending status?