MG2 rumble / vibration

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by bear4, Jan 2, 2012.

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  1. bear4

    bear4 Junior Member

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    I am still getting used to my new Prius, just have a little over 700 miles on it. I keep learning about it and this board is a great place. I recently noticed something very strange with the car - if I am in "Ready" with ICE off, and I put it in drive and release the brakes, but do not press the accelerator, the car will slowly move forward, just like a regular auto transmission. After about 1 second the speed will reach about 2 mph and I can feel a very small rumble in the cabin and a very light vibration on the steering wheel. It sounds like a very low frequency bass, and it lasts for less than a second. It goes away and the car continues to accelerate up to about 5mph (the accelerator is still not pressed). This sound is almost unnoticable, and it does not happen if I release the brake and immediately press the accelerator, it only happens while creeping forward very slowly. I was able to make this sound/vibration last longer by "riding" the breaks and keeping the speed around 1-2 mph, it is very faint and I have realy listen to it. Anyone experienced this? Any ideas what is causing it? To me I believe it is caused by some resonance/harmonics in MG2 turning at extremely low RPM, at least it "feels" somewhat "electric"...
     
    #1 bear4, Jan 2, 2012
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  2. qbee42

    qbee42 My other car is a boat

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    Rolling forward with your foot off the gas comes from a feature called "automatic creep", which simulates the creep developed by normal automatic transmissions. Toyota wanted to keep the driving experience of a Prius as close as possible to normal cars.

    As for low speed vibration, you could be experiencing some cogging in the electric motor. It's also possible that you are experiencing rumble from the road surface and tires.

    All cars tend to have some vibration like this, but normally it is masked by the noise and vibration of the engine.

    Tom
     
    #2 qbee42, Jan 3, 2012
  3. bear4

    bear4 Junior Member

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    No, it is definitely not the tires or road surface, electric motor is most probable cause. I guess it must be normal...
     
    #3 bear4, Jan 3, 2012
  4. GrumpyCabbie

    GrumpyCabbie Senior Member

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    Easy way to check. Go test drive another Prius to see. If it does it too then it's normal, if it doesn't then get yours checked.

    The Prius does emit all sorts of weird noises (esp when new) thought most of the ones I remember were high pitched hums from the inverter.

    Whilst I have your attention - go check your tires psi's and make sure they're spot on to the manufacturers recommendations (some drivers go a few psi over these) and you will get the best mpg's out of your new car. The Prius seems to run a few psi higher than most 'traditional' cars so dealers don't always set them correctly.
     
    #4 GrumpyCabbie, Jan 4, 2012
  5. eric1234

    eric1234 Active Member

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    #5 eric1234, Jan 4, 2012
  6. bear4

    bear4 Junior Member

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    I found that having the tires spot on makes the car a bit bumpy compared to my wife's 2010 corolla, and I like a smoother ride, I actually keep the tires couple of psi lower than recommended for a smoother ride, but not low enough for TPMS to come on...

    Went to the dealer and test-drove another 2011 prius today. Noticed that it had the same rumble / vibration at very low speeds with accelerator released, so I think it is normal... It is actually very hard to notice this effect, you really have to listen to the car and feel it. The sales person did not know what I was doing and looked a bit alarmed until I was able to explain him....
     
    #6 bear4, Jan 4, 2012
  7. Kb2lzh

    Kb2lzh Junior Member

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    I have the same thing with my Prius.
     
    #7 Kb2lzh, Jan 6, 2012
  8. bear4

    bear4 Junior Member

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    I have a friend who works at Toyota service department in the nearby city. Went to that dealer today and test drove 3 different Gen 3 Prii. The rumble described in this thread occured in 2 of them. I was also told by their Prius mechanic that this is a known design issue, but very few people notice it, and even fewer actually complain about it. Toyota won't do anything about it unless more people complain, so I am asking to please post on here and let me know if you have this issue in you Gen III.
    Conditions:
    1. ICE off, system is in Ready, foot on the brake, shift is in D
    2. Release the brake but do not press the accelerator
    3. The car will start creeping forward
    4. At about 1 mph you will feel a very slight vibration on the steering wheel and a very soft rumble through the body of the car. You have to be on the smooth road with heater/AC and radio off, windows up
    5. Same will occur in Reverse
    Please report here!
     
    #8 bear4, Jan 12, 2012
  9. adamace1

    adamace1 Senior Member

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    My car does this. I'm not worried my car still makes alot less noise/vibration than most other cars that are always burning gas to cover up tiny noises, and vibrations. You have to be feeling for it, and you would never notice if you were burning gas.
     
    #9 adamace1, Jan 12, 2012
  10. bear4

    bear4 Junior Member

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    You are right, you won't be able to notice this rumble in a regular car with gas engine running. Prius is so quiet that you notice every little noise. Regardless, I was told that this issue is due to MG2 design and toyota won't redesign it unless people complain.
     
    #10 bear4, Jan 12, 2012
  11. El Dobro

    El Dobro A Member

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    To me, it compares to the feeling you get with a manual trans car when you slightly lug the engine.
     
    #11 El Dobro, Jan 12, 2012
  12. bear4

    bear4 Junior Member

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    Possibly, except in a manual transmission this rumble is a lot more pronounced.
     
    #12 bear4, Jan 12, 2012
  13. qbee42

    qbee42 My other car is a boat

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    That's a good analogy. When an ICE lugs you feel each cylinder fire. With an electric motor, you feel each pole pull into place. The cause and effect are similar.

    Tom
     
    #13 qbee42, Jan 12, 2012
  14. adamace1

    adamace1 Senior Member

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    Do you really think they need to fix this?

    Do they then need to make the brake pump silent cause it makes some noise to? I also noticed the laser on the cd player makes noise when i put a new disc in.
     
    #14 adamace1, Jan 13, 2012
  15. bedrock8x

    bedrock8x Senior Member

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    If this is a Lexus hybrid, they will. For Toyota Prius, no.

     
    #15 bedrock8x, Jan 13, 2012
  16. bear4

    bear4 Junior Member

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    I think they should fix this as it is a ride quality issue, IMHO

    So far we have 4 reports of this rumble issue in this thread. Anyone else?
     
    #16 bear4, Jan 13, 2012
  17. bear4

    bear4 Junior Member

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    Update - went to the selling dealer yesterday and complained about this issue to their service manager. Apparently, they've never heard about this problem, but were receptive. I had the service manager and 2 of their prius technicians ride in the car with me. All three of them confirmed the problem, but currently there is no solution from Toyota. We then took 2 more brand-new prii from the lot and drove them. They had the same rumble too.

    We even test drove a Camry hybrid and it had the rubmble as well, although a lot less noticable, possibly due to softer engine mounts...

    The service manager told me that at this time they cannot do anything about it as it appears to be "normal" for this vehicle; however, they told me to call Toyota USA and log this problem in their system. If enough people complain about it, Toyota my issue a TSB for this problem.
    At the same time I had them fix a small rattle inside the driver's door and disable reverse beep, so it was a productive visit. Please post in this thread if your Prius has this rumble or not. I will call Toyota USA next week and really want to have more data from other people!
     
    #17 bear4, Jan 15, 2012
  18. qbee42

    qbee42 My other car is a boat

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    I haven't felt the rumble, but from the descriptions in this thread it sounds like the problem is unreasonable expectations. This doesn't sound like a real problem, or something that can be fixed with a TSB.

    If it bothers you, by all means complain to Toyota. It's your right as a consumer. They may be able to take it into account on future designs. But I wouldn't hold my breath waiting for a fix.

    Tom
     
    #18 qbee42, Jan 15, 2012
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  19. bear4

    bear4 Junior Member

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    I believe Gen II does not have this issue, it is only in Gen III.
     
    #19 bear4, Jan 15, 2012
  20. qbee42

    qbee42 My other car is a boat

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    The designs are similar, but the Gen III has a geared MG2. Normally I would expect that to reduce the sensation of cogging, but mechanical resonances and such can be quirky.

    Tom
     
    #20 qbee42, Jan 15, 2012
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