Rough Engine Start/Stop when in P

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by iact0, May 14, 2022.

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  1. iact0

    iact0 New Member

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    May 14, 2022
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    Vehicle:
    2007 Prius
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    Hello everyone! I have a 2nd Gen Prius with 151,000 miles that has been well maintained and driven in Tennessee for most of its life, so very little rust. I have had this car for about 2 years now, and I have noticed that sometimes when the engine starts or shuts off while the car is in park, the entire car seems to rock and shake. In particular the engine seems to shut off very roughly, sometimes rattling the entire car. At idle the engine runs very smoothly, this issue only seems to happen when it switches on and off to run the generator and charge the battery.

    The only problem that I am aware of right now is that the left axle seal is leaking slightly, but not enough to even drip on my garage floor, and when the fluid was checked last week it was still full. I have kept on top of maintenance as best I can (transmission fluid inspected every 30k, oil changed and checked regularly, new spark plugs, etc) and the car drives very smoothly, so I’m not too concerned, but I have been keeping a close eye on it to make sure it doesn’t get any worse as I worry it may be an issue with the generator or the transmission. Is this something common, or should I be worried? Thanks for the help!
     
    #1 iact0, May 14, 2022
  2. ChapmanF

    ChapmanF Senior Member

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    To some extent it's just the nature of the beast. The way the transaxle works, the torque that's used to start the engine has to be braced against the wheels, and in Park that means the car can bonk against the parking pawl (there's an inch or two of car travel possible within a parking gear notch). You can minimize that effect by also applying the parking brake when in Park (the brake uses friction rather than a pawl in a notch, so it holds the car more still).

    I've noticed my Gen 3 even applies the hydraulic brakes via the ABS actuator whenever it's about to start or stop the engine. I had a Gen 1 before, which definitely didn't do that, but I don't know if they added that trick in Gen 2 or not until Gen 3.

    The engine is designed to idle at 1000 RPM, and operate at that speed or above, or be stopped. They tune the rubber engine mounts and other stuff in the car to have resonances somewhere below that, so the normal operation of the engine feels nice. But it always has to go through that resonant range on the way from 0 to 1000 and from 1000 to 0, so they try to pass through as quickly as they can, but a bit of shake is unavoidable.
     
    #2 ChapmanF, May 15, 2022
    iact0 likes this.
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