W208 320 idling a bit quickly on cold start

Discussion in 'Engine' started by clk208, Sep 10, 2010.

  1. clk208

    clk208 Hardcore MB Enthusiast

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    Noticed my CLK was idling a bit quickly on the first start today - around 1300rpm.

    After about 30secs it dipped down to a more normal fast idle of around the 1000rpm mark.

    Other than this car is running fine, MPG good and no other symptoms. Once warmed up settled to the usual sub 700 rpm.

    Any ideas on what the correct fast idle should be? Is this the first signs of any particular sensor or component going awry?

    Will keep an eye out to see if this occurs regularly.

    Thanks chaps.
     
    Last edited: Sep 10, 2010
  2. tpwuk

    tpwuk Hardcore MB Enthusiast

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    That sounds completely normal! My 430 behaves the exact same way.
     
  3. momomo

    momomo Hardcore MB Enthusiast

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    Fast idle on cold start up is normal. Its purpose being to get the car up to operating temperature faster and also to get the cats warmed up for emission purposes.
     
  4. MarkJunedd

    MarkJunedd Hardcore MB Enthusiast

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    Mine does exactly the same. About 1100-1200 for about 30 secs then it drops to about 900 then when warm its about 750.
     
  5. DITTRICH

    DITTRICH Hardcore MB Enthusiast

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    I am not convinced that this is normal except under very cold weather conditions. My c230k used to start at 700 rpm in all but very cold (=0) conditions. However, it now always starts high and drops like the above car. I have not however yet found a garage who have managed to solve the question of why it is now doing it.
     
  6. tpwuk

    tpwuk Hardcore MB Enthusiast

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    It's normal behaviour. I suggest it's abnormal if it doesn't behave this way.
     
  7. OP
    OP
    clk208

    clk208 Hardcore MB Enthusiast

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    Interesting. Have owned the car since 2006 and never really noticed what goes on at idle before.

    Have been mostly riding round as a passenger in my friend's diesel golf for a couple of weeks hence why I probably noticed the CLK sounded a bit racy today by comparison.

    Outside temp was an indicated 18 degrees. Would be interested to know if they are supposed to idle more quickly at very cold temperatures.
     
  8. tpwuk

    tpwuk Hardcore MB Enthusiast

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    I suppose it depends on what your routine is. If you start your engine and then drive off straight away, you'll probably not notice the startup idle behaviour. I on the otherhand, start the engine and allow the startup idle process to complete before setting off on my journey.
     
  9. DITTRICH

    DITTRICH Hardcore MB Enthusiast

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    I have owned the car from 16,400 miles - now 147,500.
    It was put in storage once and when it came out of storage it began to start at 1,300rpm instead of 700rpm. No garage has succeeded in curing this. Prior to going into storage, it only used to start higher than 700rpm on very cold days. No other car I have seen starts at 1,300. Hence I don't think it is right.
     
  10. Nasco12

    Nasco12 Hardcore MB Enthusiast

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    I have exactly the same issue with the further complication that when I put it into drive at the higher idle speed there is an astonishing lurch.
     

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