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C220cdi Still poor mpg

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by streaker, Nov 27, 2012.

  1. streaker

    streaker Active Member

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    Your Mercedes:
    C220 Estate 2004 2.2 Diesel
    Hi

    I posted recently concerning my sudden onset of poor MPG

    I have now had the car on STAR at a recommended indy and the only fault found were 2 injectors out of spec, these have been replaced and a slight miss fire and pinking noise have gone, but she still puts out plenty of black smoke on heavy acceleration and will only do 32mpg the MAF is new and the values are good as well as the EGR.

    when the MAF is disconnected I can easily get mid 40's - 50mpg with good power and very little smoke,

    The reduction in MPG happened at sometime during a 3 day period when I was commuting only 4miles to work, I only noticed it on my normal friday night 200 mile trip home

    So must be over fuelling with maf plugged in, but what could cause this without showing a fault on the Star ?

    Please help

    Jaz
     
  2. paul hayward

    paul hayward Senior Member

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    Your Mercedes:
    all MB sold..V70R now ;-)
    try a V8:lol:....thats interesting on the MPG:lol:

    sorry cant help but good luck sorting;)
     
  3. andy@pcd-ltd

    andy@pcd-ltd Guest

    What temp does the engine run at
     
  4. bigtwin

    bigtwin Banned

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    Have you cleaned the thing? I had a prob that wasn't quite as severe as yours, but a freshen up rendered an extra 5+ mpg. Nothing form the STAR, didn't realise that it was batting below average till I trawled this site for performance figures*.





    * Massive sycophantic plug - do I win a free T-shirt?
     
  5. OP
    streaker

    streaker Active Member

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    Your Mercedes:
    C220 Estate 2004 2.2 Diesel
    Engine gets up to 90c within 4 miles from cold (recent new thermostat and coolant)

    Runs great without the MAF but is more refined and a bit more power with it plugged in just the annoying smoke and much lower mpg

    Bigtwin cleaned what ?

    Cheers Jaz
     
  6. jj1975

    jj1975 Senior Member

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    Your Mercedes:
    w203 c220cdi 2002
    Hi
    If it its smoke when you accelerate there must be air leak somewhere check the hoses from turbo to the EGR valve and the intercooler for any split or EGR valve sticking open
     
  7. bigtwin

    bigtwin Banned

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    The MAF. Isoprop the insides etc.
     
  8. OP
    streaker

    streaker Active Member

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    Hi Bigtwin

    the maf's Brand new less than 400 miles and is right on spec according to the Star readings
    but thanks for repling

    Cheers
     
  9. OP
    streaker

    streaker Active Member

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    C220 Estate 2004 2.2 Diesel
    Hi jj1975

    my indie is going to check the egr next although its fairly new and the Star reports its readings are in parameters, I cant hear any out of the ordinary turbo noise or air sound's and there seems to plenty of boost, the acceleration is very strong, could a small inaudible air leak cause 20% reduction in mpg ?
    Thanks
    Jaz
     
  10. Steve@Avantgarde

    Steve@Avantgarde Forum Supporter Authorised Forum Supporter

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    Your Mercedes:
    C220CDI AMG Line Premium, SLR McLaren Roadster, SL55 & C32AMG
    Have you had this chipped/remapped?
     
  11. OP
    streaker

    streaker Active Member

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    Hi Steve@Avantgarde

    I was told by the garage i bought it from that it was remapped (to have the dpf deleted) I believe the power has been upped as well,
    I ran the car for a month, 500 miles per week mostly motorway and was getting around 46 - 50 mpg on the motorway and around 35mpg in town on very short journeys, then suddenly it dropped to 28 - 31mpg motorway and town
    I picked it up today after 2 injectors were replaced, the mpg is still the same but there is a lot less smoke, after 40 miles I unplugged the Maf and instantly got 48mpg at 70 on the motorway
    I would happily bring the car into you as I only live 30 miles from you but unfortunately I'm working in Liverpool until end of Jan

    Cheers
    Jaz
     
  12. IceBoy

    IceBoy Senior Member

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    Your Mercedes:
    S320 CDI - W220-2005
    Sounds like an air leak.

    I had this same problem a few years ago. Problem is that air leaks can be a pain to find.

    IceBoy
     
  13. OP
    streaker

    streaker Active Member

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    Thanks IceBoy

    its in having a new heater matrix next week ( couldn't shift the restriction - Damm !!!! )

    I'll get them to look for an air leak

    cheers
    Jaz
     
  14. Steve@Avantgarde

    Steve@Avantgarde Forum Supporter Authorised Forum Supporter

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    2 things that spring to mind on this.

    The DPF pressure sensors have been modified. Even though the DPF is deleted the engine management still needs a value from this sensor so technically, its not deleted from the system. I have had a few of the 646 engines suffer poor economy because of this sensor. Now whether this would have an effect on your car I dont know, the values would have to be checked.

    The other thought I have is that of a fractured intercooler. I have a C220cdi that started black smoking a bit and it lost a bit of economy too. I had a tiny split in the intercooler, not enough for it to drop power but enough for it to play up in other ways. This could explain when you disconnect the MAF it runs better. The MAF is measuring unmetered air, when its disconnected, it runs a basic setting. On the flip side to that, its not a hot film system and disconnecting MAFs on diesels doesnt normally do a great deal.

    This is a confusing one for sure but I am willing to bet the remap and DPF delete has something to do with it somewhere if its not a leaking intercooler.
     
  15. OP
    streaker

    streaker Active Member

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    Hi steve

    It certainly seems like a component /sensor problem or an air leak
    as the economy dropped instantly, I just didn't notice it until I went on the motorway, the smoke has reduced a lot since the injectors were changed although it reduces to normal levels with the Maf unplugged,

    Can I just confirm that leaving the MAF unplugged for an extended time will not harm it or anything else ?

    Many Thanks Jaz

    Ps if i have not resolved this problem I would like to bring the car down to you in early feb to give it the once over
     
  16. Steve@Avantgarde

    Steve@Avantgarde Forum Supporter Authorised Forum Supporter

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    I cant imagine it doing any harm leaving the MAF disconnected. Just keep an eye on it.
     
  17. OP
    streaker

    streaker Active Member

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    Thanks steve

    I presume your comment re the MAF not having a hot film means it wont cause any problems with the MAF when I eventually re connect it ?

    Jaz
     

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