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2007 Prius running at 25mpg

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Bhavesh Shah, Jul 6, 2019.

  1. Bhavesh Shah

    Bhavesh Shah Junior Member

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    Recently had lot of work done on my Prius and during the time the 12 Battery died and HV Hybrid Battery died too. Had to jump start the car and since then it has been running at about 25mpg. The front wheel bearing were making noise so had them replaced. Also on startup the engine was running rough and once push gas pedal or idle for about 3-4 minutes it would run fine. Picked up this issue after filled up gas. Replaced PCV Valve, Four Injectors, Spark Plugs. Getting no check engine light and car runs fine except it runs about 25mpg. Could anything be wrong with MG set. Read on multiple forums about 12 V Battery could be issue affecting the electronics in Prius. Any help will be appreciated.
     
    #1 Bhavesh Shah, Jul 6, 2019
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. Odometer reading?
    2. Are any warning lights on?
    3. How old is the 12V battery? Is it fully-charged now? If not, charge the battery fully.
    4. Reset the mpg counter in the MFD. Take the car for a 50 mile drive on flat terrain, on a road where there is no traffic, proceed at a speed of 50 mph.

    What mpg is logged during that drive? That is going to be about the best mpg that the car can log.
     
    #2 Patrick Wong, Jul 7, 2019
    Raytheeagle likes this.
  3. bisco

    bisco cookie crumbler

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    you need a new hybrid battery
     
    #3 bisco, Jul 7, 2019
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  4. Moses Bruh

    Moses Bruh Member

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    25mpg sound pretty bad, you can try adding some techron to ur tank to see if it helps to mpg.
     
    #4 Moses Bruh, Jul 7, 2019
  5. jerrymildred

    jerrymildred Senior Member

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    @Bhavesh Shah, when you emailed me with your question, I forgot to ask what the gas mileage was before you had all that work done and why it was done. That could be a big factor.

    And, as I suggested, you might want to go back and recheck that everything was reconnected properly.

    If it was getting 25 mpg before the repairs, then I would also suspect the hybrid battery.
     
    #5 jerrymildred, Jul 7, 2019
  6. Bhavesh Shah

    Bhavesh Shah Junior Member

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    I was getting in the rang of 40-45 mpg.
     
    #6 Bhavesh Shah, Jul 21, 2019
  7. Bhavesh Shah

    Bhavesh Shah Junior Member

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    2007 Prius
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    II
    I have read the article with 12V Battery discharged causing it to lose all learn parameters. In my case my both batteries drained out. I charged the 12V Battery and even bought a new one but the results were the same 25 mpg. Do i need to drive for multiple of weeks and run few tankfull before the car computer learns new values to maximize fuel mileage. Has anyone experience 25 MPG when their 12V Battery died.
     
    #7 Bhavesh Shah, Aug 3, 2019
  8. jerrymildred

    jerrymildred Senior Member

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    If the car is OK otherwise, putting in a new 12V should only make a very small change in mpg. Maybe 5 mpg at the very most. There's still something drastically wrong. Maybe a brake dragging or something? The possibilities are bountiful, but just forgetting your driving parameters is not one of them.
     
    #8 jerrymildred, Aug 4, 2019
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