Jolt when petrol engine switches off

Discussion in 'Gen 2 Prius Technical Discussion' started by Wooster, Mar 13, 2012.

  1. Wooster

    Wooster Junior Member

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    Hi
    I've a 2004 Prius. Had it for 3 years. 40,000 miles. No problems what-so-ever. 55 to 60mpg without any effort.
    During the winter I noticed that when the petrol engine switched off - there was a jolt. (It used to be totally imperceptible.) Nothing drastic - I have to be on smooth tarmac to notice.
    My Toyota dealer said this sometimes happens in cold weather. He had no idea why.
    However, the weather has warmed up - and I can still feel the jolt.

    Don't know if it's connected, by the central display diagnostic check tells me...
    EMV. Code: 01-DC. Sub-code: 1C6-F6-1

    Any idea what's going on?

    Regards to all from the UK!
     
  2. David Beale

    David Beale Senior Member

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    Heavier oil in the engine will cause it to jerk. Don't know the code. Perhaps someone else can look that up for you.
     
  3. Wooster

    Wooster Junior Member

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    I've never heard of this connection before but as I currently have Mobil 1 in the sump - it's 0W30 - this cannot be the issue.
     
  4. Oldwolf

    Oldwolf Prius Enthusiast

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    Mine does this too sometimes. Seems to be more noticeable when he engine is cold. I am using Mobil 1 0W30 also.
     
  5. qbee42

    qbee42 My other car is a boat

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    When a Prius turns off the ICE, it burns off residual fuel and spins the ICE to stop at an optimal position for restarting. Sometimes it misses on the first attempt and has to go around for another try, producing a rougher shut down. This is more likely to happen with a new or cold engine.

    Tom
     
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  6. Oldwolf

    Oldwolf Prius Enthusiast

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    That's interesting. How is the optimal position calculated? Maybe the position is such that none of the pistons are on the compression stroke (is that even possible?) so to give more time for crankshaft spinup before encountering compression. Might make for a smoother ICE restart.
     
  7. jim240

    jim240 Junior Member

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    I thought it did this as the car finished its inital warm up. Phase three or something the hyper milers call it.
     
  8. qbee42

    qbee42 My other car is a boat

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    It does, as well as any other time when the ICE shuts down. The shutdown after initial warm up is the first opportunity.

    Tom
     
  9. David Beale

    David Beale Senior Member

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    There is a crankshaft position sensor in the engine. Cold or heavier oil will mess up the "estimate" the system uses to have the engine stop close to the correct position. This causes it to miss and do a "go around" for another try. When Pearl was new it sometimes took three or four tries to get it right. She makes it on the first try most times now.
     
  10. Wooster

    Wooster Junior Member

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    This is absolutely fascinating guys. Really interesting stuff. But is there a fix for the problem for when the ICU misses the correct 'stop' position and goes around for another try? (It's about 14c -57F- where I am and I'm using the thin 0W30 oil.)

    And does anyone know what the error code is all about:
    EMV. Code: 01-DC. Sub-code: 1C6-F6-1
     
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