rapping noise after spark plug change

Discussion in 'Gen 3 Prius Technical Discussion' started by KEN KESEY, Feb 24, 2018.

  1. KEN KESEY

    KEN KESEY New Member

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    Have 2010 Prius IV--110-k miles--ran beautiful until I changed plugs the other day.

    Replaced with iridium Nippo Denso--same exact plug as was in it and they were original.

    As soon as I started it engine started to rap like a bearing kind of.

    I took all 4 back out to make sure they were the right original plugs--they were the same as i took out--checked gap as well.

    Used my scope to look in at top of piston in case something fell in--they are very clean and I use synthetic oil. As soon as I started it--rapping sound more from the front right facing the engine.
    Any ideas very much appreciated--its not a bearing--cant find anything on you tube--all ignition coils and boots are fine
     
  2. AzWxGuy

    AzWxGuy Weather Guy

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    Could be a misfire, and might be cylinder 3 or 4 considering where you are hearing the sound. Did you disconnect the electrical plugs on the spark coils when you removed them to get to the spark plug down below? Maybe they aren't connected back up correctly, or connected to the wrong coil. To early maybe to get a misfire code, or you would need to get the codes read to see that. I would check connections and make sure the correct wiring harness plug is attached to the correct spark coil.
     
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    That's probably not on: I don't think it's physically possible to mix up the connectors; they're all very short, directly adjacent to the coil they connect to, and they have a positive locking mechanism.

    I'm wondering if it's just the proverbial knock-on-startup, but that's probably wrong too.

    All I can think for next step, and I believe someone else did this here with success:

    put the old plugs back in.
     
  4. 12voltman

    12voltman Member

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    I dont think its causing your knock problem, but the original Denso plugs Toyota installed in the Gen 3 Prius , have been superseded to a hotter plug. They are both iridium , but the new plug # , is hotter .
    They were a Denso SC20HR11 from facory.
    The new superseded plug is a Denso SC16HR11

    You will likely only find these new plugs at a Toyota Dealer . I think mine were about $12. each !

    june-2017-product-bulletin-supersessions-within-the-spark-plug-range







     
    #4 12voltman, Feb 24, 2018
    Last edited: Feb 24, 2018
  5. KEN KESEY

    KEN KESEY New Member

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    I thought of that but Only unhooked one and put it back on---I just went outside now that's its dark and looked for arcing like the old days when plug wires were bad---but none ?
     
  6. KEN KESEY

    KEN KESEY New Member

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    Your right---I thought of that to but there all in line--pretty hard to screw up---guess who threw the old plugs out--I only can find 2--but the next post makes sense to---not sure what to do right now
     
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  7. KEN KESEY

    KEN KESEY New Member

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    It does sound more like a misfire---the darn plugs are identical to the 2 I saved--height--series-brand-model # like you guys said.
    I will never throw old parts away again until up and running
     
  8. audiodave

    audiodave Active Member

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  9. AzWxGuy

    AzWxGuy Weather Guy

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    There won't be any visible arcing since the high voltage path is about a half inch long down inside of the hole the plug sits in. And Mendel is right about not being able to hook up the connectors wrong because of wiring harness orientation. Impossible to get it wrong, and you only unhooked one coil from the harness. It wasn't one on the right front side facing the engine was it?
     
  10. KEN KESEY

    KEN KESEY New Member

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    No it wasn't--but it was second one from right---can they be clipped in wrong--it seemed to go right back in--are the coils finicky units--I have never replaced or unhooked one before---thanks for the info on arcing---I have one of those tools that by passes the boot---hooks to plug and the to coil a friend let me borrow.
     
  11. Danny3xd

    Danny3xd Active Member

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    Same experience here after replacing the plugs with AGKs. But knocking stopped after 30 seconds or so. That lit the check engine icon. Then disconnected pos, 12v battery for 30 seconds. (Surprisingly did not reset radio?)

    But was fine and danny after that.

    Just asking as my knocking, Rapp tap tapping on my chamber door was pretty loud and alarming. Did you let it run or quickly shut her down?

    Asking cause mine smoothed out pretty quickly but first instinct was to turn it off to check 2see what I mucked up.
     
  12. AzWxGuy

    AzWxGuy Weather Guy

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    More theories, given what Danny3Xd says. Would engine control ECU adjust spark timing for plug wear over time, and then misfire when given new, back in tolerance plugs? I let my dealer change my Gen III plugs recently at my 160K service with no ill effects. I changed my own Gen II plugs without incident. I don't think a 12V reset was part of either of those services. Hopefully all four plugs were installed properly, torqued to specification. A compression loss around a loose plug would cause a misfire. A code reader could tell you which plug it is. Used to be you would short out each plug wire from the distributor and the bad plug was the one that didn't change the misfire rhythm. Can't do that anymore.
     
  13. KEN KESEY

    KEN KESEY New Member

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    Danny---it was pretty loud--thought engine was going to blow--shut it down---next time was a little quieter but still shut it down---just went and bought another set of plugs--correct ones--same thing--took them right out and old new ones back in--rap is quieter but still loud---does disconnecting battery re set the computer--there are no codes on my dash ?
     
  14. KEN KESEY

    KEN KESEY New Member

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    Plugs are in to correct tolerance----I have a code reader but there are no misfires--I will still try that---I didn't know what Danny was meaning with the 12 volt battery disconnect---Thank you everyone so far you have been GREAT ! I miss my 65 Chevy C-10---straight 6 cylinder that had a key ignition and you could time it by ear.
     
  15. padroo

    padroo Senior Member

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  16. KEN KESEY

    KEN KESEY New Member

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    Now its showing a code finally----p303 misfire ?????

    checked clips to coil and put in 1 of the 2 old plugs and same thing---shut off code and it stays off but still misfiring
     
    #16 KEN KESEY, Feb 25, 2018
    Last edited: Feb 25, 2018
  17. padroo

    padroo Senior Member

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    Cylinder #3 misfire. I would inspect the wiring at #3 cylinder first with a visual inspection, kind of strange it started after you touched it.
     
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  18. KEN KESEY

    KEN KESEY New Member

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    Yes it is---I unclipped it--all 4 prongs are straight and it went right back in solid and clipped nice
     
  19. KEN KESEY

    KEN KESEY New Member

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    Got it----Thank you---will let you guys know !
     
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  20. audiodave

    audiodave Active Member

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