cat converter (exhaust questions)
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This is a discussion on cat converter (exhaust questions) within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; i have a stock wrx bug eye and it didn't pass emissions,the catalytic converter is not operating efficiently. i need ...

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    Registered User rpenny33's Avatar
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    cat converter (exhaust questions)

    i have a stock wrx bug eye and it didn't pass emissions,the catalytic converter is not operating efficiently. i need it to pass emissions what are some inexpensive options that i can pursue. i have a SPT bosal exhaust could that be added and correct the problem. my problem involves inefficient catalyst performance and it tells me that bank one is where the problem is at. is gutting the both down and up pipe an option. please help, i miss my car...

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    He simply abides. SD_GR's Avatar
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    If the cat isn't working, how or why would gutting it help?

    Did you fail due to a CEL or did you fail due to measured high emissions, or both?
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    Registered User rpenny33's Avatar
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    yeah it wont help much been reading up on it a little. my code was P0420 - Catalytic Converter Efficiency Below Threshold on bank one. i am stuck on what i have to do to fix this. may have to give in and get new down & up pipe. what are you thoughts on steps i should take. strapped for cash also...appreciate you answering to thread

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    He simply abides. SD_GR's Avatar
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    Quote Originally Posted by rpenny33 View Post
    my code was P0420 - Catalytic Converter Efficiency Below Threshold on bank one. i am stuck on what i have to do to fix this.
    Reverse whatever you did to generate it. Is the car modified?

    Will the car be tested for emissions or just CELs?
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    Good news, everyone! xxxxxxxAnub1s's Avatar
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    Sometimes the cat just goes bad, this is probably one of those times.

    Purchase a known good stocker downpipe from the classifieds if you're strapped for cash. If you remove the cat from the exhaust, the problem will persist, if you replace it with a high flow cat, the code will likely go away.

    One of the things you should do once you're financially able to, is replace that up-pipe if it's still a stocker, that's not where this problem stems from, but it's something that is important to do nonetheless.
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    Is it possible to gut the cat and then do the same mechanical fix that is done for a cat-less dp?

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    Quote Originally Posted by monsta121 View Post
    Is it possible to gut the cat and then do the same mechanical fix that is done for a cat-less dp?
    The mech fix just bypasses the CEL, it still won't pass emissions if they use a sniffer. No cat is not better than a malfunctioning cat for emissions

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    A catback (post cat exhaust) isn't going to solve a cat problem....

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    I have the infamous cat code. The problem is i dont know if its the O2 senor thats faulty or if its the cat thats failing. Are there two different codes, one for cat and one for the lower O2 sensor? Because everything I have read so far leads me to believe that the code for the cat and the lower o2 is the same. I was also wondering how the car knows that the cat is failing. Doesnt it have to do with the o2 sensor reading?

    Also I was thinking if guting the stock cat and doing the mech mod might work since when people but in after market DP the increased airflow from the lack of cats trips the CEL with the same code that i am getting. So if i gutted it and the ecu picked up increased flow which i then negated by doing the mechanical mod with the spark plug antifoulers, wouldnt that possibly work?

    I just bought the car so im very low on funds. My other option is gettin a ebay DP for about $80. Are those any good? Im in Texas and im pretty sure they dont do the sniffer test, just the OBDII. So thats all im worried about passing. Not really looking for power gains or anything

    BTW its a 03 wrx with a BOV and axle back exhaust.

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    Quote Originally Posted by monsta121 View Post
    I have the infamous cat code. The problem is i dont know if its the O2 senor thats faulty or if its the cat thats failing. Are there two different codes, one for cat and one for the lower O2 sensor? Because everything I have read so far leads me to believe that the code for the cat and the lower o2 is the same. I was also wondering how the car knows that the cat is failing. Doesnt it have to do with the o2 sensor reading?

    Also I was thinking if guting the stock cat and doing the mech mod might work since when people but in after market DP the increased airflow from the lack of cats trips the CEL with the same code that i am getting. So if i gutted it and the ecu picked up increased flow which i then negated by doing the mechanical mod with the spark plug antifoulers, wouldnt that possibly work?

    I just bought the car so im very low on funds. My other option is gettin a ebay DP for about $80. Are those any good? Im in Texas and im pretty sure they dont do the sniffer test, just the OBDII. So thats all im worried about passing. Not really looking for power gains or anything

    BTW its a 03 wrx with a BOV and axle back exhaust.
    My guess would be it's your cat, may be fried from the BOV causing it to run rich during shifting. If you get the money you could even go with the AP and get performance while being able to override the code, otherwise I think gutting the DP and doing the bypass would work

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    Quote Originally Posted by Cephalgia View Post
    My guess would be it's your cat, may be fried from the BOV causing it to run rich during shifting. If you get the money you could even go with the AP and get performance while being able to override the code, otherwise I think gutting the DP and doing the bypass would work

    Yeah that might be it. I just bought the car yesterday. The previous owner did give me the stock BPV so ill put that on. Any write ups or guides on gutting the stock DP cats?

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    I had an aftermarket BOV when I bought my car, I bought a stock BPV and now it runs much smoother when driving. Unless you're running an a/m turbo and high boost levels it's worthless for anything but noise and some negative side-effects

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