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Low miles per gallon. MPG

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by C-in-DC, Mar 1, 2024.

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  1. C-in-DC

    C-in-DC Member

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    Need some help troubleshooting mpg. In the past two weeks my miles per gallon consumption has dropped from 41(that’s too low) to 36. My average miles per gallon is at 17. I cleaned the intake manifold and was going to clean the EGR but the obd2 reading of 21 kpa indicated it was still clean from when it was newly installed last year. Rule this out?

    I checked my rear passenger side wheel bearing and it’s pretty stiff compared to the rear driver side (I replaced that last year). Could this be the cause? Drag?

    I’m using 93 gas instead of 87 and occasionally smell fumes in the car when I got the heat on. Could this be a dirty MAF sensor? I don’t feel rough idling. I don’t get a drop in strength either.

    Does using premium gas cause issues? Should I replace the fuel injectors ? This engine is from 2016 via a swap and I used the existing fuel injectors since my 2010 fuel injectors were insanely dirty.

    the bottom panel got broken from road debris years ago. I have not replaced it. Could this be contributing?

    is suspension the likely culprit or engine issues? Is there a test to check the catalytic converter efficiency?

    btw, no codes except the tire pressure light that came up yesterday. Will be filling them and checking the pressure soon.
     
  2. C-in-DC

    C-in-DC Member

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    Preliminary
     

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  3. Tombukt2

    Tombukt2 Senior Member

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    Things will add up but those things shouldn't add up to this doesn't seem like injectors just all of a sudden it's possible there are various methods to cleaning them IV connections that can tie into your fuel line or something to blow them out taking them out and sending them out to be ultrasonically cleaned or doing it in your own ultrasonic cleaner maybe I haven't done anything like that and many years and haven't seen my gas mileage fall off quite this bad usually when it starts to falter It's usually the battery is acting up or something like that but fuel delivery will do it but usually when they get clogged up and so on this start missing and skipping running poorly something.
     
  4. C-in-DC

    C-in-DC Member

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    Hybrid battery or 12V?
     
  5. Tombukt2

    Tombukt2 Senior Member

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    I mean I would be looking at the hybrid battery for a gas mileage lost but I would think 10 or 12 miles to the gallon My God the battery would be in pretty poor condition flashing from green to blue to magenta on the MFD very regularly like driving to the store and things like that once you see that to start going on and then you're getting pretty much high up in the HD failure arena. And of course then your battery fan will be coming on full tilt any minute The ice engine will be running pretty soon like all the time and that should put you right in the 39 gallon range 37 maybe.
     
  6. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Should that last phrase read “My average miles per hour…”?
    will the wheel free-spin 2~3 revolutions with a push? See rear brake drag in my signature (on a phone turn it landscape to see signature).
     
  7. C-in-DC

    C-in-DC Member

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    it won’t make a full rotation when I spin it so I know there’s a drag factor. I got a new moog wheel bearing arriving on Tuesday. When I replaced the drivers side last year was worse off financially so I couldn’t afford to replace two at the same time. Can do it now.

    I’ll post a photo of the dash display. If I calculate the gas used and purchased it’s pretty much on point with the dash display.
     
    Tombukt2 and Mendel Leisk like this.
  8. Tombukt2

    Tombukt2 Senior Member

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    Yeah well when you put the other side back together you just want a light drag if you spin the wheel with all your might you'll hear it go whoosh woosh woosh as the shoes go by the parts of the drum that it's adjusted to even with a perfectly turned drum and brand new shoes you will not get it even perfect drag the complete rotation of the wheel usually You will hear it where it catches the drum the leading or trailing shoe doesn't matter I actually adjust mine so that I can get a light drag factor almost all positions on the rotation if it's done carefully If you get it too tight it's a disaster you'll have to loosen it a little
     
  9. PriusCamper

    PriusCamper Senior Member

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    I've seen one tire with low pressure cause this problem... Boost your tire pressure as high as you're comfortable with and then a little higher than that. Not sure why you haven't cleaned MAF sensor yet?

    For now, I'll blame it on you buying a bad tank of gas and it being middle of winter when MPG is always bad. I also blame it on loss of capacity and need for reconditioning of your hybrid battery pack: http://www.hybridautomotive.com/frequently-asked-questions/
     
  10. C-in-DC

    C-in-DC Member

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    Photo of dash.
     

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  11. C-in-DC

    C-in-DC Member

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    Hybrid battery and 12v battery
     

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  12. C-in-DC

    C-in-DC Member

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    I got a green bean battery in 2018 or 2019. It threw a code last year and they replaced it in the summer. My warranty is “lifetime” so I’m not sure what that means for them. If it’s that I can’t technically reach out to them till it throws a code from what I remember.

    I will definitely monitor things with the tire pressure back up to normal again.

    I haven’t cleaned the MAF sensor since last year. I don’t know how often it should be cleaned. I replaced the map sensor last year and my wallet regrets it.
     
  13. PriusCamper

    PriusCamper Senior Member

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    Yeah... it's just your hybrid battery... Once you get warning lights Green Bean will come out and put a new one in.
     
  14. C-in-DC

    C-in-DC Member

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    I got green bean on a recommendation from my old mechanic. Had I known about priuschat then I would’ve gotten oem and tried installing it myself.

    voltage should be up to 18 ? I don’t remember the hybrid battery threads too well. Guess that’ll be tonight’s reading
     
  15. PriusCamper

    PriusCamper Senior Member

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    Also on East Coast these folks appear to be major players in the market: Mobile Hybrid Battery Replacement Repair | Hybrid Battery 911
     
  16. C-in-DC

    C-in-DC Member

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    So the tpms light was on the dash and I checked the pressure of all the tires. They’re all pretty much at 35 psi(I don’t do 33 psi on the rear). The light indicator stayed on the dash even when I readjusted each tire’s psi. When I scanned the car, I found no fault codes but the indicator was clearly on the dash. The freeze frame was cleared out and it went away.

    guessing the wheel bearing threw the tpms indicator light? Maybe my pressure gauge is broken? Don’t think I had any issue with the tpms having more than 33 psi at the rear tire.
     
    #16 C-in-DC, Mar 4, 2024
    Last edited: Mar 4, 2024
  17. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Batteries going on the sensors?

    ours are “ok”, but once in the last year the light went on, stayed on a few days, then inexplicably went off.
     
  18. JeffAnd

    JeffAnd Junior Member

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    Common causes of poor fuel economy.
    1 Low tire pressure
    2 Driving fast ( over 70 mph)
    3 Repeated jackrabbit acceleration.
    4 Excessive weight in the vehicle (400 pounds or more.)
    5 Brakes dragging. Check brake temperature after a drive.
    6 Excessive cold temperatures ( especially below zero temps)
    7 Driving is snowy or icy conditions.
    8 Check engine light.
    9 Engine oil level to high. (Check the dip stick)
     
  19. C-in-DC

    C-in-DC Member

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    Fuel consumption yesterday
     

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  20. C-in-DC

    C-in-DC Member

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    IMG_1406.jpeg It’s hovering around 49-50 mpg consumption and averaging 18 mph. haven’t been using the heat as much because it’s been warm here. The Weather and tire pressure effect are that drastic? Wow.

    will post info after I replace the wheel bearing.