How far have you run it since this happened?
A good run on the highway might help, but if it doesn't you may
be looking at an oxygen sensor rather than the catcon.
Now, I have experienced that some cars, particular some Chrysler
Corp models, are harder on converters than others. Some of those
things just collapse internally.
No, but a good long highway drive might get the thing hot enough to burn
out contamination. Then again, it might not.
It might also be possible to drop it, clean it out with acetone, and put
it back. Then again, it might not.
"C'est un Nagra. C'est suisse, et tres, tres precis."
anything acetone can dissolve, heat will burn so no point using it.
when run too hot because of raw fuel dump, the catalytic metal wash
diffuses too deep into the ceramic matrix for it to work. i'd clear the
code, then go for an italian tune-up. if the code returns,
check/replace the sensors, and if they don't resolve the prob, replace
The surface of the cat's element is wispy, like cotton candy. That gives it
a tremendous amount of surface-area for the physical volume of the element.
Remember that cats work on adsorption principles, not absorption.
When excess amounts of raw gas are admitted to the cat, the wisps overheat
and melt, just like when cotton candy gets wet. This action (called
"sintering") greatly reduces the available surface area, and thus the
effectiveness of the cat. That's ultimately what sets a P0420 on cars with
excess HC going into the cat.
The cat is meant as a clean-up device ONLY; its life depends on proper
combustion in the first place.
yes it's porous, but cotton candy, it ain't. imagine you had a bucket
of pebbles, and you stuck them all together with a wash of pva glue.
there would be holes between the pebbles that you could pass liquids and
gasses through, but they're stuck together at their contact points to
give them the function of a larger contiguous solid on the macro scale.
no "wisps", just lots of very tiny pebbles.
well, adsorption is certainly part of the catalytic process, but
catalysis is not simply adsorption - the glass in your windows are
exposed to air for instance, and they have an adsorbed layer of air
molecules as a result [and lots of other stuff] - but there is no
catalysis going on.
ok, sintering does indeed reduce surface area, but it's one heck of a
stretch to call it melting, even on the micro scale. and sintering is
not the only thing going on to kill the cat's efficacy.
"sintering" is most commonly a diffusion process which happens in the
very very briefly, if you have two solid pebbles touching, and you heat
them [but to a temperature well below melting], you'll get diffusion at
the contact point, and that forms a bond. if sufficient [function of
time and temp], that bond can hold large structures of these pebbles
together, which is where pottery and "ceramics" come from. the longer
and hotter the heating process, the more diffusion, and more
densification. [that's why cheap cups and plates weigh less than
expensive ones. and why overheated pottery sags and deforms because of
there are "sintering-like" processes which involve micro liquefaction,
but they're not employed in auto catalyst substrate manufacture afaik.
[these cites below are kind sorta there, but they're technician-grade
and don't adequately explain the relevance and mechanism of the
automotive catalytic converters can handle a lot of abuse. what they
can't stand is poisoning, e.g. lead or other agents, or overheat for
prolonged periods. poisoning kills them because the reagents get bound
into compounds that are no longer catalytically active. excess
heat/time kills them because the surface wash of reagents diffuses into
the substrate and reaction rates slow to the point of ineffectiveness.
that's also why a leaking head gasket can kill a cat, especially on a
honda where it can go unnoticed for an extended period - silicates coat
the cat surface "burying" the active metals.
no, catalysis is /not/ adsorption! adsorption is all about us all the
time and nothing happens. catalysis is catalysis and that's very
special because stuff /does/ happen!
are hard cookies "whispy too? because sintered ceramics are just like them.
i did actually explain the wash and the diffusion mechanism that binds
the ceramic particles, but you snipped it. the composition of the
ceramic substrate isn't particularly relevant provided it meets physical
requirements and doesn't react with the catalytic agents.
that's not a representative example - solid state with a considerable
void percentage is by far the norm. there are some sinters that have a
liquidus phase, but they're usually the applications where they don't
get much high temperature use.
Oooh, bad, BAD. Raw fuel like that is death to the cat.
Depending on how long you've been driving it that way, the raw fuel may
have sintered the cat's surface to the point where it fails the OBD-II
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