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O.T. Gutting your cat.

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  • O.T. Gutting your cat.

    I have a 2005 silverodo V6 with bad catalytic convertors, and have been thinking of gutting them out. Is this a good idea, what problems can I create, how will the truck run. I know this is illegal but it is just a thought.

    Jon
    SW Mi

  • #2
    It'll run fine, but with a check engine light on. The down stream O2 sensors will pick up that the catalyst isn't doing it's job.

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    • #3
      Also might be illegal!

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      • #4
        Oh thank god --- ready the topic and thought you off'ed the kitty for something to chow on --- was going to say you can always eat dust mites but glad you don't have to go through what I went through with that,,,

        What Paul said in post two --- it's new enough to have an upstream Oxy sensor and a downstream (from the cat) so the downstream will send a signal to the computer that nothings changed and toss a code out on the dash ... you can always pull the bulb lol good luck

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        • #5
          If you have a downstream O2 sensor then yeah the computer won't like it. I would get a good cat from a wrecking yard.
          25 miles north of Buffalo NY, USA

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          • #6
            Originally posted by nickel-city-fab View Post
            If you have a downstream O2 sensor then yeah the computer won't like it. I would get a good cat from a wrecking yard.
            A legit yard can't sell you a used cat.

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            • #7
              Originally posted by paul463 View Post

              A legit yard can't sell you a used cat.
              News to me, didn't know that. I wonder who got that law passed? and how much they paid for it?
              25 miles north of Buffalo NY, USA

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              • #8
                the car will stink and be louder.

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                • #9
                  Convert that pig to electric.
                  http://pauleschoen.com/pix/PM08_P76_P54.png
                  Paul , P S Technology, Inc. and MrTibbs
                  USA Maryland 21030

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                  • #10
                    Originally posted by Cheap Jon View Post
                    I have a 2005 silverodo V6 with bad catalytic convertors, and have been thinking of gutting them out. Is this a good idea, what problems can I create, how will the truck run. I know this is illegal but it is just a thought.

                    Jon
                    SW Mi
                    As I understand it, the car is not likely to run as well with the 02 sensor sending a fault to the computer. The car does a lot of adjusting of timing, fuel and airflow to get the most that it can out of the engine while staying clean burning. Without the information from the 02 sensor many will use default settings. Or so I've heard.

                    Dan
                    At the end of the project, there is a profound difference between spare parts and left over parts.

                    Location: SF East Bay.

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                    • #11
                      That should be correct.

                      The system is designed to run "closed loop" to satisfy certain conditions at the O2 sensor. Without the feedback, the system is programmed to go into "limp home" mode, where the gas mileage and emissions are potentially way out of spec, but the thing does "run".

                      It is not intended to run like that for long, and as an OBDII vehicle, if you have emissions requirements, it will flunk the very simplest of inspections instantly, with an un-addressed "service engine soon" flag..
                      CNC machines only go through the motions.

                      Ideas expressed may be mine, or from anyone else in the universe.
                      Not responsible for clerical errors. Or those made by lay people either.
                      Number formats and units may be chosen at random depending on what day it is.
                      I reserve the right to use a number system with any integer base without prior notice.
                      Generalizations are understood to be "often" true, but not true in every case.

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                      • #12
                        in my (limited) experience the lack of a proper signal from the rear sensor will not put the car into limp mode, it will just set the mil. it might depend on which ecu the car has. besides you could probably trick the ecu with a simple resistor.

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                        • #13
                          If the catalytic converters are bad as you say, are they bad due to being plugged or just ineffective triggering the check engine light?
                          Removing or gutting a plugged converter will initially allow the engine to produce more power due to the loss of restriction the plugged cat caused.

                          However doing so will likely trigger the ECU to send out a fault code lighting the check engine light due to the post cat O2 sensor receiving skewed info in regards to fuel trims not being consistent with what it presumes is a non-functional catalytic.
                          The ECU does not know that the cat has been removed and so adjusts fuel trims up or down in order to meet the prerequisite specs built into the ECU's fuel map, or it will at least try to as it's range of adjustment is dependent on the presence of a functional cat .

                          How negatively this will affect engine performance, longevity, and fuel mileage can only be ascertained by driving the truck under various conditions while observing the fuel trim readings on an OBDII scanner that is capable of displaying this info. Plus you will have to interpret those readings in order to give yourself the knowledge to make an accurate assessment of your course of actions in regards to to allowing the engine to operate under these new operational parameters.

                          You could just run it as is and either ignore the check light or remove it, but then you would be oblivious to any further warnings it might want to relay to you. Also without any other info from fuel trims or an exhaust gas analyzer (basically and wide band O2 sensor) you are just flying by the seat of your pants.

                          Who knows, you could get lucky.
                          Home, down in the valley behind the Red Angus
                          Bad Decisions Make Good Stories​

                          Location: British Columbia

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                          • #14
                            How did you determine the cat(s) are bad? What codes do you get?
                            No passing inspection in many states with any type of engine or emissions OBD code or "Systems not Ready" either.

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                            • #15
                              Originally posted by Corbettprime View Post
                              Also might be illegal!
                              You can actually gut a cat without it being "detectable" as in "intentional"

                              the recipe is simple - if you have a four banger pull a plug wire and ground it to the engine - if you have an 8 cly pull two and do the same --- now hop in and go for a quick full throttle high RPM drive, you will overheat the cats ceramic's and blow it out the tailpipe (or it will end up in the muffler and rattle around for years,

                              you could also ignite the undercoating on the cars belly - you could also start a forest fire,,,, so bad idea - this is "just in theory"

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