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Eco Mode - (Stop-Start) Jerking/Jolting/Jumping C250 CDi 2012

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Cheerybloke, Jul 7, 2019.

  1. Cheerybloke

    Cheerybloke New Member

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    Your Mercedes:
    2012 C250 Cdi Coupe Blue Efficiency
    Mercedes Eco Mode "Sart-Stop" function problem.

    I have recently purchased a 2012 C250 Cdi Blue Efficiency with Eco Start-Stop function with the 7-g auto box. While I accept this feature is a bit like "Marmite" and you either like it or not, so its either permanently switched off if you don't like it, or, like me, it's left on when driving in cities/towns. (Personally for me I find when driving in towns or cities where inherently you get a lot of start-stop traffic I think it's a useful feature to have so have it switched on for this type of driving).

    My question is, when the system works and all the system parameters have been met and the car comes to a standstill and switches the engine off, when its time to move off again and I release the brake pedal the car "jerks/jolts/jumps" as it re-engages the forward gear, (similar to putting a manual car in gear with the revs at about 800rpm and the clutch half out). It does this whether I use the "Hold" function and gently press the accelerator or, simply hold the car using the brake, when I release the pressure off the brake pedal. I'm getting no fault codes or warnings on the dash when it does this so as far as I'm aware no fault codes are being recorded in the system computer. It's annoying as I thought it should be smoother when releasing the brake pedal. Has anyone else experienced this and, is this common on Mercedes or do I need to get something reset/fixed? For some reason it doesn't do this if I come to a halt, the engine switches off and I select reverse, it then engages reverse gear and starts with no jolting, jumping or jerkiness.

    I bought the car from a MB Specialist reseller. The car has a full MB service history and the seller had the ATF changed the week before I picked the car up at a MB main dealership as it was at 70k and needed doing in accordance with MB service schedule. Following the ATF change MB reset the gearbox using their Star machine.

    I've not had the car more than a couple of weeks so couldn't say if it has always done this, but since owning it these last two weeks every time it goes into Eco Stop-Start mode it does this. The car is under warranty so if I need to have something changed, repaired etc I'd like to get it done under the sellers warranty.

    Has anyone experienced anything similar and has any idea as to what may be the issue. I've been told it could be the Torque Converter, the auxiliary oil pump that keeps the oil circulating in the gearbox when the start-stop function is active and switches the engine off, and it could even be the batteries, both the main and the smaller battery that manages the Start-Stop and Hold functions.
     
  2. Tony Dyson

    Tony Dyson Senior Member

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    2014 C 220 CDI W204 OM 651
    Hello and welcome to the forum!

    I have the same 722.9 AT and Blueefficiency Stop/Start and it behaves nothing like you have described, I have experienced nothing but smooth take off and gear transitions in every scenario, the only exception is if I am too eager and touch the accelerator before the vehicle has completely started from a stop at say a road junction then it will surge to catch up, I have just shy of 50k Miles on the clock and my first ATF change is due on my next service.

    Interesting that you say 'Following the ATF change MB reset the gearbox' What was the reason, and what exactly did MB reset in the gearbox?

    On a car with such a provenance and bundled with warranty, I would waste no time at all and insist it is something that needs MB's attention.
     
  3. OP
    Cheerybloke

    Cheerybloke New Member

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    2012 C250 Cdi Coupe Blue Efficiency
    Thanks for the welcome and for your reply.

    Apparently, and according to the "Master" Technician at MB, after every ATF change they reset the gearbox on their Star Machine which is the same as resetting the TCU which learns your individual driving style and adapts the gearbox to suit. It's standard practice apparently.

    I fully intend to get the car back to the MB Specialist reseller next weekend who is aware of my problem and has been since I drove the car home after purchasing it from them a couple of weeks ago. Obviously I took the car for a good test run before I bought it but ironically at the time it didn't get into Eco mode. I can only assume some of the many different parameters that must be met in order for this system to operate hadn't been met. To be fair to the seller he has been nothing but accommodating in his approach to getting the fault rectified and is arranging for the car to be taken into his local MB dealer who also did the ATF change before I picked the car up.

    Like you have said, it is not unreasonable to expect a MB with the Eco Start-Stop function to operate smoothly and not in the manner which mine is. I thought in the interim I'd ask the question on here to see if anyone else has experienced anything similar.
     
  4. CowleyStJames

    CowleyStJames Senior Member

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    Your Mercedes:
    Mercedes-Benz C-Class Estate C200 CDI BlueEFF. Executive SE 5dr
    Mine went in for an ATF and filter change at its last service with MB.
    Whilst at it they downloaded the latest software to the gearbox, 7g+.
    This righted a slightly jolty gearchange that it's always had.
    However my stop/start function has never behaved anything like yours is.
    I do wonder if it's worth you resetting the gearbox as letting it relearn.
    Ignition on, accelerator hard to the floor for ten seconds. Ignition off, accelerator up and leave for at least ten minutes. This will wipe the last learnt driving pattern and it'll then learn your driving pattern.
    Not convinced it'll help with your stop/start issue though. But worth a try.
    Can't believe the dealership uses Star to carry out the relearning process when it's so easily done with the method I've explained. Are you sure they didn't apply a software update as they did with mine?
    That would need Star
     
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  5. OP
    Cheerybloke

    Cheerybloke New Member

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    Hi,

    The dealership used Star to reset the gearbox as that's the method they always use. When asked about the "other" way to reset the gearbox as you've described in your post, they knew nothing about this method and simply stated why they would need to reset it that way when they have a machine that's perfectly capable of doing it.

    I have already reset the gearbox TCU using your method as I knew about this already from my previous MB. It has done nothing to cure the jerky Stop-Start. I think the only way to cure my problem will be through the MB Dealership.
     
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  6. Tony Dyson

    Tony Dyson Senior Member

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    I was of the belief and I don't recall where I read it unfortunately, that the 722.9 box learning algorithm is restarted every time the engine starts from an ignition start, surely they don't expect the first driver of a vehicle to be the only driver within the ATF change schedule periods? and if there is a manual reset for new drivers why isn't it in the OM?
     
  7. Gazwould

    Gazwould Senior Member

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    ATF should have been changed in 2017 .
     
  8. Tony Dyson

    Tony Dyson Senior Member

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  9. Gazwould

    Gazwould Senior Member

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    Can't see it on there , however it's dated.. as is handbooks frozen in time , for the up to date latest , consult a dealer's service dept or two .

    5 years / 77,500 miles .
     
    Last edited: Jul 7, 2019
  10. Tony Dyson

    Tony Dyson Senior Member

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    P. 23 40,000 mls or 4 Years and the book is as old as the car!
     
  11. LostKiwi

    LostKiwi Senior Member

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    The so called reset of the gearbox by using key off throttle down etc is a fallacy. At best it may reset the throttle position sensor but it does nothing to the gearbox.
    There are two potential resets they may have done:
    1. Reset TCU error codes. This would make sense.
    2. Reset transmission adaptations. This would not make a lot of sense as the adaptations are there to account for wear in the gearbox and an ATF change won't change the amount of wear.

    OP - I'd be taking it back. Start stop should be transparent in operation as if it annoys people they'll just turn it off which is not what manufacturers want.
     
  12. Gazwould

    Gazwould Senior Member

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    No 651 !
     
  13. rf065

    rf065 Senior Member

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    Pretty sure the 40,000/4 years is for the 5 speed & 77,000/5 years is for the 7 speed.
     
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  14. CowleyStJames

    CowleyStJames Senior Member

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    Can't imagine it does that as it'd almost be pointless having a learning box
     
  15. Tony Dyson

    Tony Dyson Senior Member

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    Gentlemen, all classes besides M and CLK as per the snippet below, changed at 40k or 4 Years!

    upload_2019-7-7_19-50-58.png
     
  16. CowleyStJames

    CowleyStJames Senior Member

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    Not true, I've done mine numerous times and the gearbox is a totally different beast after

    http://www.mercedesmedic.com/reset-mercedes-benz-transmission-procedure-instructions/
     
  17. LostKiwi

    LostKiwi Senior Member

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    Did jack on either of my 722.6 equipped cars nor on my previous 2.

    You'll find the exact same procedure posted for BMW, Audi, VW....
    Which given they use different gearbox and ECU/TCU manufacturers I'd find hard to believe.
     
  18. Tony Dyson

    Tony Dyson Senior Member

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    Well the truth is I simply don't know, but the theory of a constantly learning algorithm is not new, we all have them in our intelligent home heating/cooling systems and so many other applications.
     
  19. Frosty149

    Frosty149 Senior Member

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    My e350d’s - both of them, have been super smooth on stop/start operation 1st one was a 7g, new one a 9g, incidentally 40k atf change and I don’t care what the manual says!
    Beware of short fluid changes too (the TC gets ignored!).
     
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  20. Tony Dyson

    Tony Dyson Senior Member

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    As well as I believe the Heat Exchanger! :shock:
     

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