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Oil in Throttle Body: Normal?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Rebound, Jul 6, 2016.

  1. Rebound

    Rebound Senior Member

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    I just did some maintenance on my 93,000 mile 2012 Plug-in: I cleaned the EGR pipe, the MAF sensor and the throttle body. When I opened the throttle and looked in, I saw something shiny. I dipped a Q-Tip in, and it's motor oil. It's pretty far down, well below the throttle plate.

    Is this normal? If not, what's the cause, and should I fix it?
     
    #1 Rebound, Jul 6, 2016
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Yes, It is normal. The Atkinson cycle leaves the intake valves open part way up the compression stroke of the engine and about 1/3 of the air/fuel mixture is expelled back into the intake manifold. This has been in contact with the oil coating the cylinder and a tiny bit of oil gets sucked into the intake manifold. It is far heavier than air and falls to the bottom of the manifold. There is no need to fix that.

    (not a Prius, but the best explanation of Atkinson Cycle air flow I found on YouTube)
     
    #2 JimboPalmer, Jul 6, 2016
  3. tankyuong

    tankyuong Senior Member

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    still need to clean it though
     
    #3 tankyuong, Jul 6, 2016
  4. Rebound

    Rebound Senior Member

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    Thank you very much! That's a huge relief!

    Should I siphon the oil out and clean it up, or will more oil just replace it?
     
    #4 Rebound, Jul 6, 2016
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    Ours looked like that too. I was a little alarmed, dipped a bit out with a syringe, then gave up. It seems a little lighter than straight oil? Not sure.
     
    #5 Mendel Leisk, Jul 6, 2016
  6. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    It will be diluted with Gasoline.
     
    #6 JimboPalmer, Jul 6, 2016
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  7. Rebound

    Rebound Senior Member

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    Do you think a turkey baster will suck it all out? They're cheap enough to throw at this.
     
    #7 Rebound, Jul 6, 2016
  8. David Beale

    David Beale Senior Member

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    If you clean it out it will just build up again. Your choice. No need to clean it that I can see.
     
    #8 David Beale, Jul 6, 2016
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  9. jadziasman

    jadziasman Prius owner emeritus

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    The oil and gasoline pooled at the bottom evaporate the next time you drive your car more than a few miles because the intake manifold gets hot enough to burn off this mixture. Most Gen 2s have this issue as well.
     
    #9 jadziasman, Jul 6, 2016
  10. tankyuong

    tankyuong Senior Member

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    I roll up paper towels and dip it in there
     
    #10 tankyuong, Jul 7, 2016
  11. Rebound

    Rebound Senior Member

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    Thanks for all of the responses. I also wrote to the experts at Luscious Garage, and they said the pooled oil is normal and they don't remove it. When cleaning the throttle body, they first insert a rag so that the solvent doesn't land in this mixture. But I sprayed the solvent on a rag and wiped the throttle body clean that way, so no fluid dropped down.
     
    #11 Rebound, Jul 7, 2016
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