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How to tell if a tuneup is needed?

Discussion in 'Gen 2 Prius Technical Discussion' started by ofsevit, Jan 29, 2010.

  1. ofsevit

    ofsevit Junior Member

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    My 2004 Prius is nearing 108K miles with no real problems so far. I have noted a slight decline in gas mileage, and I wonder with the mix of driving (half highway, half city/suburban) that we do whether we should get the engine looked at before the 150K recommended. Has anyone done this and found it to be helpful?
     
    #1 ofsevit, Jan 29, 2010
  2. efusco

    efusco Moderator Emeritus
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    What services did you have done at 100k? Do you note any wild swings in your battery's SOC?
     
    #2 efusco, Jan 29, 2010
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  3. ofsevit

    ofsevit Junior Member

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    No problems visible with the battery, and recently all I've done is oil changes and tire rotations.
     
    #3 ofsevit, Jan 29, 2010
  4. efusco

    efusco Moderator Emeritus
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    #4 efusco, Jan 29, 2010
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  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you've noticed a decline in mpg, then you've got the usual list of things to check: wheel alignment, tire pressure, dragging parking brake. Also make sure your engine air filter is not excessively dirty and your engine oil level is not overfilled.

    If all those are good, then you might consider replacing the iridium spark plugs. I just did that on my 2004 w/98K miles. Engine seems to run a bit smoother.

    Note that the engine ECU will accept a fairly substantial misfire rate before logging a DTC. For example, the Toyota repair manual, regarding DTC P030x, indicates that the DTC will not be logged until the engine ECU counts 108+ misfires over 200 revolutions with engine RPM at 1,600. The four spark plugs will collectively fire 400x over 200 revolutions (100x each plug), so this means a ~25% misfire rate is deemed OK.
     
    #5 Patrick Wong, Jan 29, 2010
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  6. Rokeby

    Rokeby Member

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    With respect to a slow. long term MPG reduction, wouldn't it also
    be SOP to check, and clean if necessary, the MAF sensor located
    below the intake air filter? :confused:

    Inquisitive minds want to know... ;)
     
    #6 Rokeby, Jan 29, 2010
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  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, that would not hurt.
     
    #7 Patrick Wong, Jan 29, 2010
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  8. Anthony bush

    Anthony bush Junior Member

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    I took my 2012 Toyota Prius into Toyota for the 100k service maintenance check, was told I needed the spark plugs changed or a tune up . Had Carmax change the spark plugs/ tune, was told it would improve my gas mileage, but I’m getting far less gas mileage.. What gives?? What happened? What’s my next move?
     
    #8 Anthony bush, Feb 2, 2018
  9. dolj

    dolj Senior Member

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    You have tagged onto a thread in the Gen 2 forum, in case you didn't realise.

    Perhaps if you ask your question in the Gen 3 Maintenance and Troubleshooting forum, you will get better answers from owners who have the same generation as you. Not all information is applicable over the different generations.
     
    #9 dolj, Feb 3, 2018
    Last edited: Feb 3, 2018
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