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Since there were a few people who responded to my cry for help, I thought I would tell what happened next.
I took the car to two Honda garages. The first one give me a quote of over £1000 but told me I would not have a guarantee for it not failing again because it could be an overfill of oil that may cause the failure of a new cat. So I took it to a second Honda garage who didn't spout this but roughly stated the same price. The only after market cat I could find was on a Lithuanian website, at a price I thought was reasonable about 450 euros. Approaching websites in UK I was told there is no market for the cat I needed and therefore no-one is making them and hence none available.
However talking to second Honda garage they told me after market parts may be the same spec but usually will not fit onto a Honda system as they should and therefore I might have the same trouble. They just don't work as well as the real thing. They would say this wouldn't they? So I bit the bullet and paid out for a new Honda cat and had very little in return for the old cat at a scrap merchant. Apparently it was really burnt out and was told the middle part was missing, which is similar to the Honda mechanic told me when I asked for the old cat.
Well after all that heart wringing, and a bank balance somewhat depleted, I now have a car that doesn't struggle up hills, drives well and a car I want to drive again. It was really hard work !
It is comforting to know the only code ever found was P0420, cat system efficiency below threshold. So i hope to run the car for another 100000 miles....... with new cat.
Anyway many thanks for the interest shown. It was appreciated.
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was told the middle part was missing, which is similar to the Honda mechanic told me when I asked for the old cat.
So the original diagnosis wasn't a million miles out?
Glad you got it sorted and thanks for coming back.
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was told the middle part was missing, which is similar to the Honda mechanic told me when I asked for the old cat.
So the original diagnosis wasn't a million miles out?
Well, depends how close you think "clogged" is to "missing".
Not very. I'd suggest.
Also depends on the extent to which you chose to believe either of them,
If a new cat fixed it, fair bet there was something wrong with the cat, but beyond that...?.
Edited by edlithgow on 22/10/2021 at 11:42
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Well, depends how close you think "clogged" is to "missing".
Bit of both really, middle collapses and blocks the exhaust gasses from exit pipe so you have a hole in the matrix which has blocked the pipe!
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Getting a bit semantic here, but words have meaning, after all.
A hole is an abscence, a vacancy, a localised lack of solid material.
Thus a hole cannot block anything.
Cats either melt or they clog with ash.
Where there is no emission check (some US states) or where there are two cats in series, one of which is not monitored for inspection (some Hondas) you can "fix them by bashing the core out with a ramrod, and people do. Bit redneck but does the job.
THAT is a hole
Edited by edlithgow on 23/10/2021 at 04:08
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Cats either melt or they clog with ash.
So they don`t break up then, odd as some have been known to break up and block the exit pipe prevent 100% gas flow, but if you say they only melt and/or clog, I will take your word for it
though I`m not talking about a bodge job, only what some failures do, what people do to unblock it is a different story....
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I can't see the ceramic honeycomb ever melting. It seems quite logical that if there is a hole in the middle, what was there has physically moved to somewhere else, causing a blockage.
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I can't see the ceramic honeycomb ever melting. It seems quite logical that if there is a hole in the middle, what was there has physically moved to somewhere else, causing a blockage.
Yes you can. Just look at the pictures I posted above.(third video in the Forumosa thread)
(Looks melted to me anyway, but I suppose I dont know it for a fact)
Edited by edlithgow on 23/10/2021 at 14:00
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Cats either melt or they clog with ash.
So they don`t break up then, odd as some have been known to break up and block the exit pipe prevent 100% gas flow, but if you say they only melt and/or clog, I will take your word for it
though I`m not talking about a bodge job, only what some failures do, what people do to unblock it is a different story....
Yeh, they break up as well, and maybe the resultant material shouldn't be described as ":ash"", but if its blocking the exit pipe it shouldn't be described as a "hole" (or "missing") either.
Here is a Honda example of a plugged non-monitored catalyst, downstream of two monitored catalysts, one for each bank of the V configuration engine. He speculates that the upstream catalysts might be breaking up and plugging the downstream, but that isn't confirmed.
www.youtube.com/watch?v=gUYk98L7umY
He explains that, since this is a non-monitored catalyst it could be bashed out without any diagnostic errors. If the upstream catalysts were working OK I suppose it might pass an emission check too, though it would not apparently be legal for him to do that.
Dunno about DIY
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I wonder if it's worth using one of those aftermarket CAT cleaners that you pop into the fuel tank, like Catalclean or suchlike?
Would it also be the case that a CAT goes bad because the car owner (or at least one of them) had mainly used it for short journeys from cold or suchlike, causing similar 'clogging' issues to that for DPFs on diesel engined cars?
£16 may be a tad expensive for a bottle of cleaning fluid (or even two of them), but it might be worth a try (if nothing else pops up during diagnostics), but it certainly beats a Grand for a new CAT or, worse still, a new car altogether...
I bought a specialist auto transmission and power steering system cleaner (about the same price) -recommended by Scotty Kilmer - and used it to clean out my PS system (which uses PS fluid) and it worked very well. Saved myself well over a Grand on a new pump, reservoir and pipework (or about £900 if just the pump were replaced).
Few dealerships will ever bother to recommend repair or cleaning of a system using a simple method because they aren't a money-spinner, especially if the car owner then can DIY it next time it happens.
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I did use a CAT cleaner after the engine light appeared. HONDA said this was the cause.....
But they would say that, wouldn't they? They put new spark plugs in because they were slightly caked. This did not fix it.
100,000 miles in 8 years does not add up to mainly short journeys.
But I think the problem began when I had to break really fiercely when another car came very quick onto a roundabout and the car went into limp mode and then recovered, which I thought was strange. That is when the light appeared.
Anyway I have to be content with what I did to solve the problem. I thought it was worth keeping the car. I don't want to be miserable..........
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But I think the problem began when I had to break really fiercely when another car came very quick onto a roundabout and the car went into limp mode and then recovered, which I thought was strange
I think that was coincidence rather than a cause, my 2016 tourer used to go limp mode after severe braking, I think system does a check to make sure all is fine before computer gives back full power then clears itself, mine did on a few occasions in similar circumstances all because some will not slow down at roundabouts which I had several near misses
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I wonder if it's worth using one of those aftermarket CAT cleaners that you pop into the fuel tank, like Catalclean or suchlike?
Would it also be the case that a CAT goes bad because the car owner (or at least one of them) had mainly used it for short journeys from cold or suchlike, causing similar 'clogging' issues to that for DPFs on diesel engined cars?.
Seems a bit unlikely. Hard to assess, because I don't know how the stuff is supposed to work, (and I'd bet they don't tell you) but any treatment added to the petrol has to survive combustion, which seems a pretty tall order.
Best (not very good) guess would be something that increases combustion temperatures (without damaging the engine? Good trick) and/or maybe an oxidising agent that helps burn off carbon in the cat, but carbon in the cat doesn't seem to be the usual problem.
Back flushing to physically remove clogging material, OTOH, (which I havn't seen recommended anywhere) isný mysterious and seems to offer a chance of clearing the exhaust system, though probably a much smaller chance of restoring catalyst function.
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People with clogged 2-stroke exhausts used to sometimes use oxy-acetylene. You got it cooking on the mix then switched to just oxygen.
You got a lot of smoke, and either a clear exhaust or a little pool of slag where it used to be.
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