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How rough is rough idle?

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Joshua Harrington, Nov 28, 2019.

  1. Joshua Harrington

    Joshua Harrington Registered

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    Joined:
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    Your Mercedes:
    C Class C220 W204 (2013)
    Hi all,

    First time poster, but found this forum thoroughly useful in the past. Thanks for all your help!

    I have owned my first Mercedes for a couple of months now and naturally im in love with it already.

    Just a niggle though- the idle is not perfectly smooth. It only jumps around about 20rmp each way, but my only experience driving diesels is double decker busses. Probably not a fair comparison!

    Is this normal for these cars, or should I look into the dreaded injector replacement?

    The car is a W204 C Class 2013 60k miles, and I got the impression that the injector problems had been ironed out. It has a full MB service history and seems very well looked after!

    If I'm being paranoid I apologise. I couldnt find anything on the forum about what constitutes a rough idle, and the car is otherwise perfect with good power delivery!

    Thanks.
     
  2. Larkone

    Larkone Senior Member

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    Joined:
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    Location:
    NW Essex
    Your Mercedes:
    CLS 320CDI 2008
    Engine mounts? - common failure on MBs
     
  3. AJD

    AJD Senior Member

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    Location:
    Suffolk by the Sea, UK.
    Your Mercedes:
    2017 W205 C200 2.0Ltr (Petrol) ///AMG Line, Premium, 4dr. Auto. Brilliant Blue with Alpaca trim
    Hi Joshua, welcome to the forum :)
     
  4. mattkh

    mattkh Senior Member

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    Location:
    England
    Your Mercedes:
    W168 1999 1.6
    Can you see a 20rpm variation on the needle in the rev counter?
     
  5. Botus

    Botus Senior Member

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    Your Mercedes:
    S500/2010/500
    find another owner and compare to theirs
     
  6. malcolm210

    malcolm210 Senior Member

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    Could be injector tip wear or slightly low fuel rail pressure but unless it starts misfiring I wouldn’t bother about it, might be worth putting some fuel additive/cleaner through it with the customary Italian tune-up

    Might be worth changing the fuel filter
     
    Last edited: Nov 29, 2019

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