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Poor gas mileage/tranny not going to high gear?

Discussion in 'Gen 2 Prius Technical Discussion' started by dawint, May 16, 2011.

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  1. dawint

    dawint Former AudiWorld Member

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    This is my first post so please bear with me!! My 08 has been getting poor mileage for the past 3 weeks or so ..... I tried a "push the power button and trip reset shift to reverse to eliminate the backup beep" mod and it did not work. However I find now that I cannot get my MPG average above 42. When I tried the mod the odometer went immediately to all bars and then the bar indicators went out one by one until the regular odometer reading came on .... I'm wondering if doing that also set the car into another "mode" where the tranny will not shift to a higher gear???? So symptoms are constant engine running when cruising to a stop and after 20-30 seconds the motor will shut off .... and while driving on the highway the engine will pick up at least 1000 - 1500 rpms just by adjusting the accelerator a smidge ..... so what do you guys think? Have the dealer scan for codes? The car is still under warranty so I'm not worried about a big bill .....thanks
    David
     
    #1 dawint, May 16, 2011
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I have good news, the transmission only has one gear, so it is always in high gear. If I was to guess, you have cleared a computer's memory so it has to re-learn how you drive the car.
     
    #2 JimboPalmer, May 16, 2011
  3. qbee42

    qbee42 My other car is a boat

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    As pointed out above, the Prius transmission is a fixed gear, non-shifting arrangement. I agree that it is most likely a learning issue.

    Tom
     
    #3 qbee42, May 16, 2011
  4. dawint

    dawint Former AudiWorld Member

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    thanks for the replies ... I know the tranny is a CVT .... but its not a fixed gear transmission its a constant variable .. all I know is that the behavior is different and that its NOT supposed to rev that high when the pedal is depressed a little bit.. and how long should it take to "learn"?
     
    #4 dawint, May 16, 2011
  5. uart

    uart Senior Member

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    Why don't you try "rebooting" it by disconnecting the 12V battery for a while and then reconnecting it. That should set it straight if it's in some kind of rogue state
     
    #5 uart, May 16, 2011
  6. qbee42

    qbee42 My other car is a boat

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    It *is* a fixed gear transmission. The Prius has no shiftable gears whatsoever. The effective gear ratios are all the result of routing power through the electrical path of MG1 to MG2. In this respect the result appears to be CVT, but it's not. Sometimes people refer to it as an eCVT to emphasize the electrical nature of the transmission.

    Tom
     
    #6 qbee42, May 16, 2011
  7. cwerdna

    cwerdna Senior Member

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    What mileage were you getting before? Did anything change about the car and your commute? About "20-30 seconds the motor will shut off", is this old a cold engine or after it's been warmed up by usage, for awhile? What if you set the HVAC system totally to off, no auto?

    If you want fuel economy help, please answer questions at:
    http://priuschat.com/forums/gen-ii-...-answer-these-questions-esp-if-youre-new.html

    How are you determining "engine will pick up at least 1000 - 1500 rpms"?
     
    #7 cwerdna, May 16, 2011
  8. bisco

    bisco cookie crumbler

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    dealer.
     
    #8 bisco, May 16, 2011
  9. mmcdonal

    mmcdonal Active Member

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    Yep, dealer. Just what I was thinking.
     
    #9 mmcdonal, May 16, 2011
  10. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Toyota calls it an eCVT. There is a fixed relationship between MG2 and the wheels. By using software, it presents the illusion of being a CVT to the driver, but there is no torque multiplication going on, it is all one 'gear'. MG1 and the ICE are each spinning at whatever speed the computers think will best use the car's resources.

    The Prius transmission is so simple to look at and so difficult for me to grasp. Frequently I think "why would anyone use anything else?' then I recall that until computers were cheap it would be impossible to control. It is not without drawbacks:
    Above 41 MPH you can't turn off the ICE without over spinning MG1
    Below about 55 MPH you can't get peak ICE HP to the tires. (below 55 you most frequently want peak torque, anyway)

    Other vendors attempts to avoid those drawbacks all seem WAY more complicated, mechanically.
     
    #10 JimboPalmer, May 16, 2011
  11. dawint

    dawint Former AudiWorld Member

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    its with a warm motor .. AC system is off .. prior to this low average I was 48-49 .. now I can barely budge 42 ..

    I'm guessing on the rev's but it it picks up quite a bit ....
     
    #11 dawint, May 16, 2011
  12. dawint

    dawint Former AudiWorld Member

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    agree ... (st) dealer :eek:
     
    #12 dawint, May 16, 2011
  13. dawint

    dawint Former AudiWorld Member

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    that's one thing I was going to try .... and I do think its in some type of "rogue" state
     
    #13 dawint, May 16, 2011
  14. ursle

    ursle Gas miser

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    Weird things happen when the 12v is dying, I agree disconnect the 12v and reconnect but if you haven't replaced it yet, do.
    And use an Optima yellow top;)

    A missing spark plug will drop your mileage into this territory, how's the power?
     
    #14 ursle, May 16, 2011
  15. snead_c

    snead_c Jam Ma's Car

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    :rockon:dealer while under warranty...:rolleyes:
     
    #15 snead_c, May 16, 2011
  16. dawint

    dawint Former AudiWorld Member

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    power's great ....runs smoothly
     
    #16 dawint, May 16, 2011
  17. dawint

    dawint Former AudiWorld Member

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    thanks for all the replies ..... now to deal with the stealer
     
    #17 dawint, May 16, 2011
  18. richard schumacher

    richard schumacher shortbus driver

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    #18 richard schumacher, May 16, 2011
  19. dawint

    dawint Former AudiWorld Member

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    #19 dawint, May 17, 2011
  20. dawint

    dawint Former AudiWorld Member

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    Follow up ... car is back at the dealer to figure out the problem (still) low MPG's
    Could be ....
    Battery (12V)
    oil overfill
    dirty MAF
    dragging brake
    car stuck in "B" mode
    205 45 17" summer stuff????
     
    #20 dawint, Oct 12, 2011
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