Car vibrating at constant speed

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by vikisonline, Feb 2, 2018.

  1. vikisonline

    vikisonline Junior Member

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    When driving around 60km/h and just above eco mode line.
    The car is slowly decellerating and i can hear the ice engine rpm drop.
    Its been around -10C if that matters.

    When it reaches a low rumble, probably around idle or lower, I can feel shaking in the steering wheel and hear a low rumble. Has happened at highway speed too. Always when the ice engine is at idle ish rpm and cruising.

    Usually when I just need a tiny ice power to maintain speed, just barely above what EV can provide.

    There are no such issues during acceleration or at idle stopped.

    2013 prius c 78000km
     
  2. padroo

    padroo Senior Member

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    If you are a DIY person I would get the car up in the air and do a visual inspection and run the car and see if you can duplicate the noise and vibration. Do you think it is engine or tire suspension related by your experience?

    If not you need to have someone look at it.
     
  3. vikisonline

    vikisonline Junior Member

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    I don't think its the suspension. My first gut feeling was maybe its the engine mount, but all other driving conditions are fine. Its almost like it hits a resonant frequency at that low rpm. The whole car buzzes with it.
     
  4. vikisonline

    vikisonline Junior Member

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    Blah, I made a video to try to record the noise but the phone was on my dashboard and other rattling sounds completely mask it... Ill try again tomorrow.
     
  5. padroo

    padroo Senior Member

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    Harmonic balancer?
     
  6. vikisonline

    vikisonline Junior Member

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    Went back to the place that put my winter tires on. Tires seem fine and checked drive shafts. everything seems ok.

    Did some more driving.
    Noticed a vibration whenever ICE is around 1150-1250 rpm. This is a mild vibration and not very bad per say. This is what I most commonly feel.

    However, whenever MG2 is around 7500 rpm there is vibration of similar frequency but much greater amplitude, regardless of ICE rpm.
    When ICE rpm is at 2000rpm and MG2 is at 7500 the vibrating gets really annoying where you can feel it in your whole body. Its a low rpm vibration, id guess around 5-20 hertz. This is usually around 95-105km/h since mg1 is practically in sync with the drive shaft. Though, if ICE rpm is not 2000, it is not that bad. This is usually a very slight acceleration or a little bit quicker slow down, keeps ICE away from 2000. So, I am not sure if quicker speed change gets me out of the harmonic range quick enough so that vibrations don't have time to build up, or if the harmonics of the ice at 2000RPM and MG2 at 7500RPM constructively interfere with each other.

    So imbalanced MG2? I read many other threads about random vibrations on here. Do you know if anyone else tracked RPMs?

    In all this MG1 rpm seems irrelevant.
     
  7. dubit

    dubit Senior Member

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  8. vikisonline

    vikisonline Junior Member

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    No its still that one. I made my peace with the low intensity one but then occasionally its bad at those rpms. so Im back and forth about being and not being worried about it.

    I have the low intensity grumbles regularly and its fine and used those to convince myself its fine. but the high intensity ones are still worrying. Needs a very specific scenario to make it happen though, but unfortunately driving in the 95-105 range is pretty common.
     
  9. dubit

    dubit Senior Member

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    Hmm, high speed. Tires?
     
  10. vikisonline

    vikisonline Junior Member

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    Possible. Ill have my winter tires taken off in the next couple weeks, and then I'll know.
     
  11. vikisonline

    vikisonline Junior Member

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    Issue is resolved.

    I been mulling over everything. Bought a new pump and a high quality pressure gauge. Turns out the fronts were 25 and the rears ~20 psi...

    Intense vibration is now gone. Fuel mileage has improved significantly. Weirdly the fronts at 25 psi just didnt look that low. Stupid thing.

    Low intensity rumble still remains, I thin that is just normal for this drive train when generating.

    Thanks guys!
     
  12. simonman

    simonman Junior Member

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    Hey, I just bought a 2014 Prius C. 112000 miles. I also notice a bad low frequency rumble/resonant/vibration when the engine has just slowed down before “coming out of” eco range into the EV range on the display. The tires were all 22 psi. They are now 44psi. The Toyota dealer balanced and performed a wheel alignment. The vibration remains. My first thought was an engine mount. I have not driven another Prius C. Is this vibration normal? In my opinion it is terrible! I had a 2006 and 2012 Prius and they had no vibrations....
     
  13. dubit

    dubit Senior Member

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    That vibration your feeling is actually normal. Kicks in right around the ECO line while deaccelerating or cruising around that point. There are a few threads on this very thing here on Prius Chat. I think I even linked to one up above earlier in this thread. While I have gotten used to it over the last 2 years, I do find myself either letting off or applying pressure ever so slightly depending on the situation in order to avoid it.

    As a sidenote, I pretty much grew up in the Toyota / GM dealership here in town and hang out there on weekends. (lots of friends still working there) and to make sure it is considered "normal" as I was told. I have test driven multiple new C's as well as any used. And sure enough, that same vibration can be found in every single one of them. Hate to tell you that though, because it's something one would think Toyota would have done something about long ago.
     
  14. simonman

    simonman Junior Member

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  15. simonman

    simonman Junior Member

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    Got it. I did test drive a 2015 C with the local Toyota tech. The 2015 did have the vibration too but was MUCH less noticeable than on my 2014. I am considering buying new engine mounts and see if that helps lessen the issue...
     
  16. bisco

    bisco cookie crumbler

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    isn't it possible to check the mounts before buying new?
     
  17. dubit

    dubit Senior Member

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    I personally wouldn’t waste the money. Especially when I know that a brand new C has the same vibration. You will get used to it and it will even become second nature to slightly apply/relieve foot pressure on the gas pedal to avoid it. Before you know it you won’t even notice it anymore.

    But if you want to drop a few hundred dollars, I’m sure the dealer & mechanic will appreciate it.
     
    ztanos likes this.
  18. simonman

    simonman Junior Member

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    The top engine mount seems pretty "soft" when pushed. I only paid $8000 for my 2014 so I don't mind spending a few bucks to try some things. Genuine Toyota mounts are pretty cheap online vs the stealership. So far I am my own mechanic when I can be. The fact that the 2015 with 90k less miles vibrated much less tells me I should be able to improve the ride a bit....
     
  19. Mendel Leisk

    Mendel Leisk Senior Member

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    Any idea how to do that? Spray them with silicon, see if something temporarily smooths out? Or check for excess play?
     
  20. bisco

    bisco cookie crumbler

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    none at all. i wonder if a look see would show misalignment?
     
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