Due to a malfunction, cylinder 3 was not firing in my auto and dumping raw fuel in the cylinder . The problem was fixed, but now the check engine light is continuously showing that the catalytic converter is defective. Does any one know of an additive that might reverse this problem? Cats are expensive (:= ]
Larry
you sure it's not just a bad O/2 sensor???
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.
--scott
iconlarry wrote in news:3084c9a4-a68d-42fa-980d- snipped-for-privacy@c26g2000vbq.googlegroups.com:
What kinda car?
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 threshold test.
What's the actual code you're getting? P0420?
Picky, picky, picky....
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 cat.
jim beam wrote in news:HKCdnbqaZK5IvmHQnZ2dnUVZ snipped-for-privacy@speakeasy.net:
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.
indeed.
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 solid state.
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 diffusion process.]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.
jim beam wrote in news:3PWdncCWr8uYgGPQnZ2dnUVZ snipped-for-privacy@speakeasy.net:
OK, porous pebbles, then. I guess "cotton candy" was too wispy an analogy.
The reactions occur on the surface of the washcoat, so "adsorption" is correct.
That page tells you nothing about the ceramic substrate, which is the "wispy" part.
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.
jim beam wrote in news:wt-dnRwda4iIMmLQnZ2dnUVZ snipped-for-privacy@speakeasy.net:
I didn't say it was. I said the reactions happen on the surface of the cat.
But the reactive portion does sinter when overheated, just like I said. Reduced surface area=reduced effectiveness.
then i was confused when you said "cats work on adsorption principles".
no, the substrate sinters, and the reactive portion diffuses.
yup. in part.
They are like hard merangue cookies.
For that matter, so are many sleeve bearings.
--scott
No, actually, they are more like a honey cake. There are big grains, but the space between the grains is filled up with liquid.
--scott
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.
In the case of the bearings, the liquid is lubricating oil.
--scott
that's introduced /after/ the sinter - completely irrelevant.
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