Oil Contamination - P0420 Cat Replacement?

Discussion in 'Gen 2 Prius Main Forum' started by Nick Petersen, Aug 25, 2017.

  1. Nick Petersen

    Nick Petersen New Member

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    A couple months ago I was having a problem with accelerating my 2004 Prius. Eventually while on the interstate my car threw the red triangle and I came to a stop. It felt like something was slipping in the engine. I could accelerate for a few seconds but eventually even when the gas pedal was pushed all the way to the floor I couldn't move. I had the car towed to the nearest mechanic and he told me that my crankshaft was drowning in oil. He fixed the problem and I took it home. The next day my check engine light comes on. I take it to Autozone and it's P0420 cat efficiency below normal (bank one). The car seems to be running fine. MPG is around 45 and I'm primarily driving 70mph everyday for 50 miles total.

    After a couple weeks of research, catcleaner, and replaced 02 sensors the check engine light is still on. Do you think it is possible that because of the oil problem with the crankshaft that somehow the catalytic converter was contaminated?

    I'm prepared to replace the cat myself and weld on an aftermarket one if I have to. But if there is a way to clean the catalytic converter that would be ideal. My car is pushing 225k miles. A brand new $1500 cat wouldn't be plausible...the local shops are estimating around $600-$700 for the repair and the catalytic converter they install will not be legal in California or NY. Instead of spending $600 I figured I would just purchase a magnaflow for $80 and weld it myself or have a shop do it. (I live in Iowa)

    Any information on the steps I can take to determine if I need to completely replace the cat would be appreciated! Thank you.

    Nick
     
  2. ih8spm

    ih8spm Junior Member

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    If you were getting oil passing through the cat it's quite possible but it could also burn off over time although I personally have never seen it happen. You should probably start by verifying the new O2 sensors are reading correctly and if money is no issue replace the cat as planned. You will have ruled out the obvious at that point. I'm in a similar situation BTW but I'm going to try foulers on the O2 rear sensor first.

    SM-G935P ?
     
  3. JC91006

    JC91006 Senior Member

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    Spend $80 for a Magnaflow and be done with it
     
  4. BigVanMan

    BigVanMan Junior Member

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    It's possible to clean the converter as I just did the same thing for my 2004 Prius with 160k miles on it (it was burning rich due to an exhaust leak). The process involves cooking your cat submerged in dilute (0.1Molar) citric acid and oxalic acid (wood bleach) solution at approximately 150 degrees for 5-6 hours. This process was taken from a 2005 study in Spain to rejuvenate old diesel catalytic converters. I did this using a stainless steel 20qt stock pot over a camp stove. I then rinsed out the cat with a garden hose, dried it out and put it back on the car. I reset the codes and the light has not come back in several hundred miles. It should help you at least pass state inspection, if that is your goal.

    The jury is still out on how long this cleaning will actually last. It couldn't hurt to try for less than $20 of chemicals (wood bleach/oxalic acid $9, citric acid $6 and 4 gallons of distilled water).

    Savogran 10501 Wood Bleach, 12 oz


    http://www.walmart.com/ip/JARDEN-HOME-BRANDS-1440055000-7-5OZ-Citric-Acid/20469602

    The concentration works out to be 76g of citric acid powder and 50g of oxalic acid powder per gallon of distilled water. Wear gloves and neutralize the acid with baking soda afterwards.

    I hope this helps clean out your cat. Let me know if it works.
     

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  5. BigVanMan

    BigVanMan Junior Member

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    Here is link to the study I based my cleaning method from in case anyone is interested:

    Regeneration of Aged Commercial Three-Way Catalytic Converters (PDF Download Available)

    A couple of things I forgot to mention. I agitated this mixture every 30 mins or so by lifting and dropping the cat assembly up and down in the pot a few times. Secondly, this mixture does remove rust as well so don't be surprised if the exterior of the stainless steel cat you put into this bath comes out rust free and somewhat shiny.
     
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  6. BigVanMan

    BigVanMan Junior Member

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    Just to update all, as I suspected, this was not a permanent solution, but in my case, the cleaning did last approximately 3k miles before the P0420 returned. This works fine for me as I now have a spare OE cat and resonator I pulled from a parts Prius. I keep one cleaned and ready for state inspections and just swap out the clean one as needed to pass state inspections. While the failing cat is off, I clean that and make that the spare one ready for the next state inspection. This has worked well for me for the past few years.
     
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