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Possible MPG increase?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Fingers04501, Aug 25, 2016.

  1. Fingers04501

    Fingers04501 Junior Member

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    Hello all!

    A while back I posted a problem i had with a cylinder misfire code. Because of all the great responses, we were a able to save hundreds on labor charges from my local shop.
    At the time, due to "budget restrictions", we only replaced the injector on the misfiring cylinder. Now that things are not quite as tight, I was considering replacing all four as PM. Currently, nothing is wrong with any of them, at least not enough to cause a CEL. It's about to roll over the 200K mark, so what I am really wondering is if it is worth doing now. Does anyone know if by doing this I can expect any return on the investment in the form of MPG increase or anything?

    Thanks for any advice!
     
    #1 Fingers04501, Aug 25, 2016
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I am a proponent of the maxim "If it is not broke, don't fix it." As you know, it will let you know when it is broke.
     
    #2 JimboPalmer, Aug 25, 2016
  3. valde3

    valde3 Senior Member

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    If you replaced one injector with new one there could be some difference in flow between that and old injectors. So then replacing the rest (with same kind of new) would get the fuel air mixture of cylinders closer to each other. That would give you a better MPG probably not measurable amount though.

    If you replaced the spark plugs after replacing the injector you could try to read the plugs. If you can see difference between the cylinder that you replaced the injector and rest of them then you need to replace the rest of injectors.

    Most likely you don’t need to do anything.
     
    #3 valde3, Aug 25, 2016
  4. Kevin_Denver

    Kevin_Denver Active Member

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    Do you have a Mini Vci cable and a computer with Techstream? I would only consider replacing injectors if I was still getting misfires. With Techstream you can view how many misfires the car has had. Normally it takes quite a few before triggering a code, so if there is anything slightly misaligned, but not so much as to cause a code, you could see the misfires in Techstream. If you don't have one already, you can consider a $15-20 investment in a Mini Vci cable.
     
    #4 Kevin_Denver, Aug 25, 2016
  5. Fingers04501

    Fingers04501 Junior Member

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    That actually makes alot of sense. Plugs were done prior to injector, Coil pack also replaced on that cylinder as well. I had noticed that the MPG dropped slowly over time prior to the repairs, and never recovered fully to the 50-ish that it had been prior to the issue. Currently it averages about 46.5 doing the exact same commute as before. Was just wondering if injectors may make that much of a difference. (Mostly a DIY tinkerer, not a master mechanic)
     
    #5 Fingers04501, Aug 25, 2016
  6. Fingers04501

    Fingers04501 Junior Member

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    I have a pretty OK OBDII scanner that shows real-time engine data. it was showing me the misfire it had initially. Does that do the same thing as the Vci cable/Techstream?
     
    #6 Fingers04501, Aug 25, 2016
  7. Kevin_Denver

    Kevin_Denver Active Member

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    I don't know your scanner, but generally OBDII scanners can only read codes. Techstream can let you read pretty much all of the data coming from the car's ECUs. I have no idea if how your OBDII scanner works is the same as Techstream. If you see this screenshot, you can see the misfire counts in the lower right:
    tech screenshot8_zpsasdvz6bx.png Photo by sonofspy777 | Photobucket
     
    #7 Kevin_Denver, Aug 25, 2016
  8. Fingers04501

    Fingers04501 Junior Member

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    Yep. Thats pretty much what mine shows. My screen is smaller, so I have to scroll through the values, but it seems like it registers the same thing. My Father in Law recommended going to our local Harbor Freight (pretty cheap discount tool outlet) when they were running a sale and i picked up one that will do everything but ABS system checks for about 69 bucks. Ive heard of people on here talking about getting an old laptop or something to run Techstream on. Is that what you are referring to? If so, i may get the cable and give it a try just because. Seems pretty cool.
     
    #8 Fingers04501, Aug 25, 2016
  9. Kevin_Denver

    Kevin_Denver Active Member

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    Yeah, you can buy a cable like this one off Amazon for $15-20, and then you just need a Windows laptop (can be installed on XP or 7, 7 just requires some additional steps which are documented online in forums if you search around). It can do lots of other things like change lock settings, lighting settings, etc, besides just reading information. I followed these instructions to get mine working and had zero problems.
     
    #9 Kevin_Denver, Aug 25, 2016
  10. tpenny67

    tpenny67 Active Member

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    I was under the impression that modern engine controls are sophisticated enough to adjust air/fuel ratio on individual cylinders, so differences in fuel flow rate shouldn't matter, assuming the old injectors are still properly atomizing the fuel. In other words it's more about quality of the spray pattern than flow rate.
     
    #10 tpenny67, Aug 25, 2016
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