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Thread: P0421 code

  1. #91
    Quote Originally Posted by 7milesout View Post
    I studied a bit. So, we have 2 cats. But my assumption is that the first cat takes all the beating and is probably 90% likely to be the one with the issue. If it were me, I would consider buying the $371 cat from rock auto. It comes complete to the manifold. However, I'm not really trusting that manifold, I'd have to eyeball the stock manifold to see how similar it is to the one pictured on rockauto.

    If I lived in a location that did not do emissions testing, I would simply pull the stock manifold and bad catalyst off, and replace it with one of the "performance" headers that have been discussed in these forums. Not for the "performance" aspect of it, but as a way to eliminate the catalyst. In littlemoule's case, if that catalyst is plugging, and he put a header on it with no cat (but a bung for 02 sensors), I think he would see rather large performance gains.

    The downside is, I think he'd be getting cat efficiency codes. Which I could live with if I KNEW that the codes were simply telling me that the catalyst that I DON'T HAVE is not working effectively ... and if the car was running good.

    littlemoule - A lot of the Magnaflow cats I saw looked like the 2nd cat in our system. So, you'd have to be sure you're getting the correct cat for fitment reasons. The Magnaflow stuff looked like decent or better quality though. The first cat (on the 2020 which is what I looked at) appears to bolt into place. No need for welding. But gonna need good impact tools to remove those bolts.
    2014-2015 have different exhaust from 2017 and newer. 14-15 have a seperate exhaust manifold where the 2017+ have the cat and manifold built together. Then the exhaust from the back of the front cat to tailpipe(which includes the rear cat) are different lengths between the 2 styles too. It's not a noticable difference unless you have the two side by side. That's why that header that you can buy for these cars doesn't fit the 2017+ style without shortening or lengthening(I can't remember which) the rear section of exhaust.

    I've heard of spark plug defoulers being used to relocate the rear O2 sensor so it doesn't read the same as the front O2 but I'm not sure if that'd work in these cars or not. They can be pretty finicky about the electromagicals.

    I have had pretty good luck removing exhaust bolts on these things but certain areas out east can turn to metal into orange dust pretty fast.


    Mirage videos:

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


  2. #92
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    Just ordered this exact one:
    https://www.magnaflow.com/products/5...onverter-53004

    Will report back if the installation is successful. May take a few days. Stay tuned my friends.

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    Fummins (06-02-2023)

  4. #93
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    I'm mildly recommending just a header. Because that's what I would LOVE to do to mine (but won't, I want to preserve the powertrain warranty and preserve the cheapness of the car). I'd love to be able to tune the fuel map, pull both cats out, and adjust mufflerage until it sounds like what I would want. Just about 50% more burble than what it has now. It would be awesome if it would sound like a Triumph triple. But I think the Triumph triple sounds good due to higher rpm.

    Our lower rpm makes the engine sound more like a Civic fartcan, so I wouldn't want it too much louder. Plus, low rpm equals low fuel consumption, so I tend to run as low an rpm as the conditions allow.

        __________________________________________

        click to view fuel log View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.9 mpg (Imp)


  5. #94
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    Sitrep: Took it to the exhaust only shop. We found the mirage has two stock CAT converters embedded deep in the chassis, one near the manifold and the second closer to the muffler. He couldn't install the universal aforementioned magnaflow cat. Next step is to take it to a mechanic to see if he can do it while ensuring the onboard computer stays happy with the new cat. Stay tuned, possibly with pictures.

  6. #95
    Why didn’t the exhaust shop do exhaust work? Couldn’t figure out how to mount a universal car or were the concerned about the car not liking the new cat?
    Mirage videos:

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


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    mohammad (06-08-2023)

  8. #96
    Quote Originally Posted by littlemoule View Post
    I will see if I can replace the plugs they are relatively inexpensive anyway. Car has 165000 km on it.
    Is it safe to say that this never happened? (I don't feel like going back and reading this 10 page thread) I'm not promoting blindly firing the parts cannon at your car but maybe start with the inexpensive parts that are already due to be replace as per service schedule...

    If you're bound and determined that you do need a cat(with half the mileage that they typically start to degrade) then maybe look into cat cleaners. I believe you dump then in your fuel tank? I think Foama or someone from the Netherlands mentioned using this kind of thing in their car?
    Mirage videos:

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


  9. #97
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    If his car is down to 22 mpg, I don't think a cat cleaner would restore it. If it is indeed the cat.

    littlemoule: 90% chance the first cat is the issue. I didn't want to say it (because you had already bought it), but the universal cat you bought looked like the 2nd cat. And looked like it wouldn't fit where the first cat goes.

        __________________________________________

        click to view fuel log View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.9 mpg (Imp)


  10. #98
    Quote Originally Posted by 7milesout View Post
    If his car is down to 22 mpg, I don't think a cat cleaner would restore it. If it is indeed the cat.

    littlemoule: 90% chance the first cat is the issue. I didn't want to say it (because you had already bought it), but the universal cat you bought looked like the 2nd cat. And looked like it wouldn't fit where the first cat goes.
    Yeah, it is the internet so....I don't buy the 22 mpg part.
    Mirage videos:

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


  11. #99
    Senior Member Mitz's Avatar
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    Quote Originally Posted by Fummins View Post
    Why didn’t the exhaust shop do exhaust work? Couldn’t figure out how to mount a universal car or were the concerned about the car not liking the new cat?
    I can only imagine the man felt a headache when he saw the proposed replacement part.. LOL



    Quote Originally Posted by 7milesout View Post
    If his car is down to 22 mpg, I don't think a cat cleaner would restore it. If it is indeed the cat.

    littlemoule: 90% chance the first cat is the issue. I didn't want to say it (because you had already bought it), but the universal cat you bought looked like the 2nd cat. And looked like it wouldn't fit where the first cat goes.
    Most commentators ruled out the oxygen sensor but I would still stick to my hypothesis that since this condition existed only after Krown rustproofing was done. There are things that can be done as I proposed before going to the conclusion that the catalytic converter should be replaced.

    What is Krown


    "The Krown oil can block or contaminate the o2 sensor reference port or the reference through the wiring and set a code, thats why people can have a problem after an application when too much is applied."

    https://forums.redflagdeals.com/krow...3/3/#p34080522

    Issues with Krown - purely coincidental?
    Krown Denied Responsibility after the fact.
    https://forums.redflagdeals.com/krow...-fact-1775833/

    Engine light after Krown rust proofing
    https://www.f150forum.com/f2/engine-...486972/index2/
    https://www.f150forum.com/f2/engine-...486972/index3/
    What is Krown

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    Fummins (06-07-2023)

  13. #100
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    Quote Originally Posted by Mitz View Post
    Most commentators ruled out the oxygen sensor but I would still stick to my hypothesis that since this condition existed only after Krown rustproofing was done.
    Uhhhhh yeaaaaah, I'm going to have to sort of go ahead and, agree with ya there. I think I'd just replace the O2 sensor and see what happens. But wait, I'm too lazy to go back in the thread, did littlemoule replace it already? Or just check it.

    If it hasn't been replaced, a new one should give years of service, so even if that's not the issue, at least the money spent is not a total waste. And, if it fixes the problem, it's a lot easier than replacing the catalyst.


        __________________________________________

        click to view fuel log View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.9 mpg (Imp)


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