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Sluggish Acceleration/Bad gas Mileage

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Darth_Eric, Jul 14, 2023.

  1. Darth_Eric

    Darth_Eric New Member

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    Recently my 2012 toyota prius with 107k miles on it has been struggling to accelerate, and is only getting 30 MPG. I've had it about a year, and have changed the tires, changed the oil every 5K, and put in some fuel injector cleaner. Im in the middle of a heat wave in central Texas temperatures above 100 degrees. One thing i noticed is when the sun goes down it seems to operate a little smoother but no improvement in gas mileage. Wheres a good place to start for Maintenance? Im not sure what maintenancehas been done on this vehicle, and its been running great up to this point. Im thinking one or all of the following should be done soon.

    Replace Spark Plugs
    EGR Intake cleaning
    Transimission Fluid change
    Clean Battery Fan

    I'm not very skilled mechanically how much can i expect to pay for each one of these services as i can probably only afford to get one of two done at a time based on price. Thank you for the help.
     
  2. Tombukt2

    Tombukt2 Senior Member

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    Need to get a competent mechanic to run a scan and check for head gasket seepage or leakage known issue for these motors be prepared
     
  3. taxidriver50005

    taxidriver50005 Active Member

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    I would suspect battery may be overheating and not giving you much assistance, check the battery fan is clean.. It is an easy DIY and it doesn't take much to clog up and affect cooling.

    Posted via the PriusChat mobile app.
     
  4. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    You'll need the plugs before long, but you might still have 6 months. Do not buy online, Amazon and eBay are swamped with counterfeits.

    The EGR has no direct impact on MPG or acceleration. I won't say it is unimportant, but it doesn't urgently bear on this situation.

    Transmission fluid: forget about it, won't help a bit. Maybe do it in the spring if you're bored and have extra cash then.

    Check/clean battery fan: do this right away yourself, youtube shows you everything. If you don't own a vacuum, head down to the DIY carwash place with a roll of quarters and a screwdriver to help with the panels and ducts.
     
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  5. PriusHead05

    PriusHead05 Member

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    I agree. Just get them from the dealership. They are even usually cheaper there than the denso ones at the local parts store.

    I might disagree on this one, but I'm not going to be definite on that. If the egr is clogged, then it probably would hurt MPGs, especially if there oil in the intake manifold and all the ports are clogged. That's how mine was. @Mendel Leisk might provide some more insight on the EGR.

    Transmission fluid exchange on mine helped the car accelerate smoother. Probably not helping with MPGs, but it is a good maintenance item. It was only $149 at the dealership. I didn't want to mess around with that one.

    YES, YES, YES! Very important. You don't want to ruin your Hybrid Battery.
     
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  6. PriusHead05

    PriusHead05 Member

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    That would be good to do too.
     
  7. Eddie25

    Eddie25 Active Member

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    Clogged EGR runners in the intake can definitely effect MPG and performance, but I don't know if it would be described as sluggish as much as rough running. Does high RPM's help at all? If not, then it's probably not that.

    If the plugs are original I highly doubt that's it, those Denso iridium's can last for 200k+ easy. Not to say they aren't worth checking, especially if the car was bought used, or if they have been changed.

    I would absolutely monitor the battery temps and see if you can tell any performance differences when it's hot or cool. if you get the Hybrid Assistant app you can set your fan to high speed and see if it helps get temps down (mine barely helps). My battery gets to 125F easy without any performance issues. When I've seen it really high I do feel like the car is a little sluggish. I doubt a clean fan will help much, but I'd still get it done if you think batt temp is the issue. Also, make sure you are running the A/C as much as possible.
     
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  8. Mendel Leisk

    Mendel Leisk Senior Member

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    Heavy AC use? Any extended idling in parking lot with AC?

    In addition to tips above: cleaning throttle body might help. Probably in conjunction with EGR/intake manifold cleaning.
     
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  9. Darth_Eric

    Darth_Eric New Member

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    Yes lots of AC use
     
  10. Darth_Eric

    Darth_Eric New Member

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    I’ll start with cleaning the battery fan hopefully that helps. I do notice when I’m driving it seems quieter then before. Any tips on getting access to it? I’ll probably just watch a YouTube tutorial. What’s the best way to clean it once removed?
     
  11. Darth_Eric

    Darth_Eric New Member

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    Should I be running the AC at full blast to help keep the battery fan from getting to hot?
     
  12. Louis19

    Louis19 Active Member

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    Well , your location indicates a hot location , my advice ,use AC for your confort , if you are good in the car , then the battery is happy:cool:
     
  13. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I agree with @Louis19 above. "full blast" may or may not be necessary, but generally if the driver is comfortable then the battery is also being cooled adequately.... assuming that the cooling fan is working and ductwork isn't full of dog hair.
     
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  14. PriusHead05

    PriusHead05 Member

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    I replaced my original plugs at 216k mi. on my 2012. They were still fine. :D
     
  15. Darth_Eric

    Darth_Eric New Member

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    What tools and products will I need to pull the battery fan out for cleaning?
     
  16. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I don't know that you even need to remove it. The primary tool for cleaning one is a powerful vacuum cleaner, and maybe a reach attachment for it.

    Our car is the c model which has a different set of ductwork... the only other tool we need for ours is a flat screwdriver for dealing with the plastic popper fasteners. I couldn't say if your liftback model is much different; never did one of those.
     
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  17. Noahdoge

    Noahdoge Active Member

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    This is the video I used. I took out the three small screws that hold the two pieces of the fan together and alternated between two cans of air. It made it much easier to clean. Just take your time with it, and don’t forget to shop for one of those clip on filters. I also would recommend you get Dr Prius app and one of their recommended Bluetooth obd to get a better idea on what’s going on with the hv battery.
     
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  18. Darth_Eric

    Darth_Eric New Member

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    Ok thank you all for the help I got in there and cleaned the Battery fan. Should I noticed a difference in MPG and acceleration, and battery staying full more often even in this insane heat?!!
     
  19. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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  20. ASRDogman

    ASRDogman Senior Member

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    For the Hybrid Battery Fan Filter
     

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