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Replaced Spark Plug going bad too early

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by kamrul, Jul 10, 2021.

  1. kamrul

    kamrul Junior Member

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    All good people!

    I changed the original plugs ( SC20HR11 ) a few months ago at approximately 90K kilometers. Replaced those with DENSO VCH20 Iridium Tough plugs but after about only 5K kilometers, the new plugs look like this.

    upload_2021-7-11_0-16-57.jpeg

    upload_2021-7-11_0-17-7.jpeg

    upload_2021-7-11_0-17-18.jpeg

    upload_2021-7-11_0-17-30.jpeg

    I am not comparing directly but my 90K kilometers run plugs do not look much worse than these. As I am thinking to replace the plugs again, I am wondering about the cause of these new plugs going bad so early at only 5K kilometers / 4 months.

    I bought from a DENSO authorized reseller. But the part of the world I live in, I won't completely discard the possibility of even an authorized reseller mixing a few counterfeit parts with genuine ones.
     
  2. privilege

    privilege Active Member

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    what's wrong with them ?
    the scorched ceramic ?
     
  3. kamrul

    kamrul Junior Member

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    Not just the ceramic, the tip looks quite burnt.
     
  4. JC91006

    JC91006 Senior Member

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    The plugs look ok, more of a problem with your car
     
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    Toyota recommends Denso SC16HR11 now (slightly hotter than SC20HR11). Not available where you are? Also, they might be counterfeit.
     
  6. rjparker

    rjparker Tu Humilde Sirviente

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    The plug is bad with blowby leaking up through the combustion chamber to the ceramic. Most likely counterfeit.
     
  7. kamrul

    kamrul Junior Member

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    This is what I have found on a recent DENSO Spark Plug Catalog for my Gen 3 (2013 Japanese Domestic Model)

    upload_2021-7-11_9-50-4.png

    Though I have got SC20HR11 in my vehicle, probably the catalog was updated later with SC16HR11 installed in 2014 or 2015 Gen 3.

    I could not find SC20/SC16HR11 at the time of replacement. Just imported a new set of plugs now - VCH16.
     
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  8. kamrul

    kamrul Junior Member

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    Any insight on what the problem could be?
     
  9. rjparker

    rjparker Tu Humilde Sirviente

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    The plug is bad. It is leaking.
     
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  10. JC91006

    JC91006 Senior Member

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    You can search "spark plug indicator" and you'll see what the plug is telling you
     
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  11. Samuel Williams Jr

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    Well I don't know crap about "counterfeit spark plug's?" So as far as "reading the plug's go?" You most likely lost that opportunity when you tossed the OEM plugs.

    So at this point, your looking at more "symptom's." Assuming the plug's are "counterfeit?" Then they have mostly taken out more system's? The plug wires would be shot, and since they are Coil on Plug. Then most likely the Coil Pack's also? And since the plug's are now "Carbon Fouled," the O2 sensors would also be suspect? As well as the MAF or Map ( I don't know which the Prius uses?) and the Cat is in danger.

    You need to also check the codes with a OBD II, code reader, to see what else is going on in the ICE? But it's a GEN 3. And most likely unless you have already done it? The EGR, Valve and EGR Cooler are full of sludge? And that could have been the source of the failure of the "OEM," plugs?

    In any case "reading plug's," looks like this.
    Reading 101: How to Read Your Spark Plugs - OnAllCylinders
     
    #11 Samuel Williams Jr, Jul 12, 2021
    Last edited: Jul 12, 2021
  12. ASRDogman

    ASRDogman Senior Member

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    That plug looks fine, best you can see from the photo's. The browning is normal.
    99% of the plugs have that, it's just the heat.
    The tip looks like it's still there, the electode hasn't wasted away.
    Were you getting codes of a misfire? Why did you pull them?


     
  13. Samuel Williams Jr

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    Those plug's look normal, Ok then. :)
     
  14. Grit

    Grit Senior Member

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    o_O
     
  15. privilege

    privilege Active Member

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    it's out of focus, but looks normal. the chocolate/mocha color you see on the ceramic under the ground strap is an indicator of very good mixture/combustion. look up "stoich spark plug" and you'll see what I mean.

    I did notice some white/ash coloring on it though. that's usually indicative of using unneeded fuel additives or possibly (but I doubt) leaded aviation fuel.

    the dark ring above the steel (towards the coil on plug connection) cool be leaking, but I bet it's just regular old oil burn in on the plugs.

    as far as counterfeit.... nah

    do you have misfires or combustion related codes ?
     
  16. ASRDogman

    ASRDogman Senior Member

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    Real or Fake Toyota parts???
     
  17. OptimusPriustus

    OptimusPriustus Active Member

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    Xenon bulbs and spark plugs.. better be carefull when buying