Is this normal?

Discussion in 'Gen 2 Prius Technical Discussion' started by Toddwilks, Dec 30, 2020.

  1. Toddwilks

    Toddwilks Active Member

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    This isn’t my first rodeo with a Prius nor my first with this one. I bought this 09 not running and had to have the complete dash harness replaced to get it working. I had the dealer do the work since I didn’t have the time to do it. I got the car back and lately I’m getting 40-42mpg when I normally get 50-52 in my 07. Same tires, same psi. I changed spark plugs, PCV, cleaned the MAF, throttle body, and checked the HV battery and it’s at 67%. There are no codes stored and the 12v is brand new.

    When I drive the car, I feel like I need to be in the gas more to get it going vs the 07 so I lifted the car and noticed that only one wheel spun. I also noticed that when I drive, it looks like I’m getting no help from the hybrid battery as it always shows charged. Check out my two videos. Is this normal or could something be making the car feel like it’s dragging? I also replaced all pads and rotors and lubed the slides.









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    #1 Toddwilks, Dec 30, 2020
    Last edited: Dec 30, 2020
  2. bisco

    bisco cookie crumbler

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    how many miles on each?
     
  3. Toddwilks

    Toddwilks Active Member

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    09 has 84000 07 has 132000


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  4. bisco

    bisco cookie crumbler

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    it doesn't make sense that the battery wouldn't fluctuate. any idea what happened to the car that required the harness?
    at 84k, it should run like new, barring an accident, flooding, rodents, abuse and etc.
     
  5. jerrymildred

    jerrymildred Senior Member

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    I wouldn't expect them to spin identically, but it looks to me like you have some brake drag or other friction going on in the left wheel. I think that the engine revving when you stopped the right one supports my guess. I'd try keeping it in ready and putting it in neutral so I could feel and compare the resistances.
     
  6. Toddwilks

    Toddwilks Active Member

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    Car would sporadically not turn on. Headlights worked, brakes lights interior lights all worked but wouldn’t see the ignition button sometimes. They found a short in the harness and also replaced the HV ecu, ignition ecu and start button.


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  7. Toddwilks

    Toddwilks Active Member

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    That’s what I thought too. Maybe a stuck caliper. That’s what lead me to do the pads rotors and lube the slides. The issue persists.


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  8. ChapmanF

    ChapmanF Senior Member

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    My recommendation for these sorts of possibly-dragging-brake issues is always to (1) confirm there's a drag (you can use a test like this, all four rotors should be stone cold at the end), then (2) if you find a corner (or more than one) that's dragging, next step is some careful detective work to find out why. There are some ideas for that also in that linked post. A lot of ink gets spilled about new pads, new rotors, or greasing the slide pins as a sort of healing ritual, but it's more dependable to just find out why that particular caliper is dragging, and then correct that. Binding can also involve the fitting kit (the little springy clips that hold the ears of the pad, they come with a dry Teflon-like coating from the factory but it doesn't last forever), or rust of the grooves that those clips sit in, squeezing the clips down harder on the pad ears.

    One thing that's too easily forgotten is that the whole fact that the caliper piston retracts at all when you release the brakes depends on the elasticity of an internal rubber seal:

    [​IMG]

    The return can be measured (I'm used to seeing about 0.3 mm when good). The key is testing with minimal force, such as puffs from a blow gun. Forces from the braking system itself are too powerful and the effect to be measured will be lost in stretching and squishing.

    Needless to say, if there isn't that piston retracting effect from the seal (some remanufactured calipers will test out as nonretracting, right out of the box), nothing else is going to fix the brake drag.
     
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  9. Toddwilks

    Toddwilks Active Member

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    Would old trans fluid cause this? I’m trying to narrow down besides a possible bad caliper.


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  10. bisco

    bisco cookie crumbler

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    no, the tranny fluid is lifetime
     
  11. mr_guy_mann

    mr_guy_mann Active Member

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    You have two cars, one that is "good", and one that is problematic. I would suggest that you log some data from both cars under the same driving conditions with Dr Prius and see what if anything is different between them. I would also log data from the engine and hybrid drive ecu's as possible- techstream would be good for that or possibly Torque pro. If the two cars don't accelerate the same then it should reflect that in data somewhere. Then you can figure out a diagnostic direction.

    Things that could cause poor performance and mpg are things like: dragging brakes, incorrect wheel alignment, weak HV battery or motor problem, ICE problem like restricted exhaust, low compression, etc.

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    #11 mr_guy_mann, Dec 31, 2020
    Last edited: Dec 31, 2020
  12. Toddwilks

    Toddwilks Active Member

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    Tranny fluid is not lifetime. It’s to be changed every 30-60k on second gen. I didn’t think it would cause it but have been thinking what else it can’t be.


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  13. Toddwilks

    Toddwilks Active Member

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    I don’t know how to see if a caliper is really stuck other than spinning a wheel freely. The car will coast fine if I put it in neutral. I have DR Prius and there’s no logging feature. I also have OBD fusion (iOS version of torque pro) and there’s no way to see brake caliper pressure to see if one is being squeezed more than the others. I did the test notated above and all rotors were cool to the touch.

    Any idea what it could be engine wise/where to look?

    Am I looking for something in particular on techstream? What should I be logging?


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  14. ChapmanF

    ChapmanF Senior Member

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    If all rotors are cool to the touch, then it seems you've eliminated brake drag as a cause. There was a link above with a technique for measuring caliper piston return, in case you need it for something in the future, but it seems to be moot for present purposes. Onward to other, non-brake things.
     
  15. fotomoto

    fotomoto Senior Member

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    The 09 wasn't used nearly as much as the 07 and its battery's poor(er) performance may be the result. It would be a lot of work but swapping battery packs between the two would be interesting.
     
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  16. edthefox5

    edthefox5 Senior Member

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    Like Foto says poor mileage and your into the gas pedal more to make up for it is usually battery. Which is very very common look at all the battery posts on this site including me.
    The fact its so low miles is a big strike against you And your Doc prius agree's with me.
     
  17. Toddwilks

    Toddwilks Active Member

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    I just ordered a mini vci cable to run techstream. Is there a particular log or screen I should look at? The 07 has a brand new oem battery and still ran better than this with the original battery with same maintenance completed.


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  18. jdenenberg

    jdenenberg EE Professor

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    Toota ATF is "lifetime" if you define 150k miles as end of life. I tend to keep my cars longer than that so I do drain and refill my Prius ATF every 60k miles.
     
  19. Skibob

    Skibob Senior Member

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    The gen 2 Prius has limited slip differential? That's the only way both tires would spin at the same rate.
     
  20. ChapmanF

    ChapmanF Senior Member

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    No fancy differential, but it does have traction control able to apply a brake on the faster-spinning wheel, to much the same effect.
     
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