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99 Misfires and P0420 Code

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  • 99 Misfires and P0420 Code

    99 Misfires and P0420 Code
    Last edited by RORDOG; 02-03-2010, 11:48 PM.

  • #2
    Re: 99 Misfires and P0420 Code

    Components wear and fail on the GX just like any other car. It may very well be the cat, as the diagnostics point towards. There is nothing on the GX that makes it immune to Cat failures.
    1997 Factory Crown Victoria w/ extended tanks ~~ Clunkerized!
    2000 Bi-Fuel Expedition --> ~~ Sold ~~ <--

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    • #3
      Re: 99 Misfires and P0420 Code

      Misfires, if allowed to continue for any length of time, can fowl the catalytic converter. The GX uses a special 3 stage cat, from what my service dept tells me. This is to keep the NoX at the proper levels and tends to be more expensive.

      I believe the emissions warranty on the cat is 8/80. Although your miles are low you have gone beyond the time allowance from the "IN Service" date of the vehicle. The dealer can tell you what the "In Service" date was for your car.

      A repeated theme I have seem in the forum is that bad wires and fowled injectors are the likely culprit on the '98 thru '00 models and cracked coil packs and injectors on the later models, although there can be other sources for the problem.

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      • #4
        Re: 99 Misfires and P0420 Code

        I have a 2000 - same generation civic. Fix the misfires first - with such low miles I'd suspect ignition problems. My first (primary) cat failed around 80k when the coil shorted. I had the random misfire problem at about 140k for months until I replaced the primary oxygen sensor (after changing out plugs, wires, cap, and coil first -- still cheaper than a visit to the dealer service dept.). Just replaced both catalytic converters and O2 sensors at 205k. If you need the replacement cat or other parts - get them from Majestic Honda online hondaautomotiveparts.com they are original OEM parts, but they charge much less than full retail price. My dealer wanted $1200 for the secondary cat - Majestic was around $700.

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        • #5
          Re: 99 Misfires and P0420 Code

          After playing with stuff since it it the market, I'll just repeat what others have said. When the engine starts running rough, with or without a MIL, get the thing fixed, or you'll be buying a CAT. On vehicles with an established history you might want to change some of the components just for the hell of it. 100k miles is a littl long for plugs, 15k miles is a long for oil changes even with CNG and synthetic oil. Thing detiorate with use or non-use.

          We used to change plug and points every 20k miles, before the car started running rough. Yes it may be a little more expensive, but how many plugs, wire, coils, injectors, O2 sensors etc. for the price of a CAT, especially if you do it yourself. CATs can several hundred thousand miles if you keep the running correctly Also what is increased reliability worth??

          Some will disagree with me, but it's just a another point of view to take or leave

          Larrycng

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          • #6
            Re: 99 Misfires and P0420 Code

            Do you have to buy this Cat at Honda? Or can you get it at Autozone or some other chain? Maybe save some cash.

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            • #7
              Re: 99 Misfires and P0420 Code

              As of this time, any replacement CAT is required to a California Air Resources Board Executive Order (E.O.) Number and has to meet Calif emission warrante requirements. To avoid possible SMOG check problems, if you go with the aftermarket CAT keep all of the paper work and a copy of the catalog page. Yes, a little overkill, but it may save you problems in the future.

              Also it is illegal for a muffler shop to install a not compliant (something without an E.O. # or OEM) CAT on a OBD II compliant vehicle

              If the cost is close I would go with OEM CAT.

              Your decision

              Larrycng

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              • #8
                Re: 99 Misfires and P0420 Code

                the code 420 refers to the secondary o2 sensor which monitors the the cat efficiency. if u replaced the cat already u might want to check the 02 sensor itself. areas to look for the misfire would be anything from bad igntion(i.e distributor, cap, plugs, etc) or even injectors.
                98 civic gx - the hov lane runner
                97 supercharged mustang - 440rwhp gas hog
                02 pathfinder

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