37mpg average 250K miles, batteries and trans 100K miles

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Bryan Holloway, Aug 31, 2018.

  1. Bryan Holloway

    Bryan Holloway Junior Member

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    Our prius is struggling and im trying to figure out why. My wife drives it so I only notice drops in MPG over longer periods of time when I get in it. It slowly went down from 46-48 to 40, and now 36-38. The engine is burning oil and is probably on its way out.

    The transmission and the batteries were replaced by Toyota at 150K miles. We have good filled tires and new optima battery, no engine codes or lights. I cant imagine the batteries or the trans going bad so soon, but am wondering if its possible. I watch the battery gauge and it seems very stable. It doesn't keep running when parked. Would the engine lose power at such a high mileage enough to bring the mpg down?

    Also, spark plugs were replaced about 50K miles ago.

    Im about to take a trip and will start with running some injection cleaner, 91 octane gas, and check the air filter.
     
    #1 Bryan Holloway, Aug 31, 2018
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. What does the engine air filter look like?
    2. What is the engine oil consumption rate?
    3. Have you had engine compression readings taken? If not, this would be a good time to do so, to assess the basic health of the engine. Toyota Techstream is needed to spin the engine at an appropriate rate (if you do not use software control over the hybrid vehicle ECU for this test, MG1 will spin the engine too quickly to have good compression test results.)
    4. Even if the engine compression is OK, if the engine oil consumption rate is high, the catalytic converter may be plugged up so that the engine cannot breathe adequately, which would reduce engine power output.
     
    #2 Patrick Wong, Aug 31, 2018
  3. audiodave

    audiodave Active Member

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    #3 audiodave, Aug 31, 2018
  4. Pdaddy

    Pdaddy Member

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    Is there any way too know the cat is going bad besides cutting off to see if symptoms go away or simply replacing? That is a difficult call to make if your engine may be on the way out.

    SM-G920V ?
     
    #4 Pdaddy, Aug 31, 2018
  5. Jmack111

    Jmack111 Member

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    Vvt solenoid valve left side of engine right by the manifold
    OEM Part Number:15330-21011

    Posted via the PriusChat mobile app.
     
    #5 Jmack111, Aug 31, 2018
  6. bisco

    bisco cookie crumbler

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    'i'm trying to figure out why'

    'the engine is on the way out'

    'i'm about to take a trip'

    (n)
     
    #6 bisco, Sep 1, 2018
  7. TMR-JWAP

    TMR-JWAP Senior Member

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    Typically a severely plugged cat will result in poor engine power. Also likely to get a P0420 code.

    When you say it's struggling, do you mean struggling due to lack of power or just struggling to get decent mpg?

    What are your wife's recent driving habits? Has she changed her normal driving distances? Does she do only 5-10 minute trips? This easily results in mpg in your range.
     
    #7 TMR-JWAP, Sep 1, 2018
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