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Effect of vacuum leaks on throttle response

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by Slacky28, May 7, 2013.

  1. Slacky28

    Slacky28 New Member

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    Location:
    Aylesbury
    Your Mercedes:
    C220 S203 modified to 175 PS
    Any thoughts before I spend money at a MB Dealer?

    I have recently acquired a W203 2001 C220 CDi Estate Auto which I am surprisingly passionate about.

    And this unexpected passio has led to me blowing 3 times the budget I had set aside to bring this 173k-er back to scratch. From Cleaned out EGr's and Autobox to new antiroll bars and rust removal/repainting.

    But it does have an annoying, potentially dangerous trait of waiting for a couple of seconds when at stanstill between hitting the throttle and the old dear actually moving.

    On the sunny bank holiday just gone I met a man (a mechanic) who knew and had driven the car, who felt that this may be a leak in the vacuum system. His hunch at the headlight adjustment end?

    And in turn, issues with engine components such as the wastegate which might account for the slugish (at best) reaction to the lights turning green.

    Anyone?
     
  2. television

    television Always remembered RIP

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    Your Mercedes:
    2002 SL500, 216 CL500, all fully loaded
    Yes Diesel do not have a vacuum system on the engine, you have a pump driven from the engine to operate the lamps and other things.

    So not that
     
  3. OP
    Slacky28

    Slacky28 New Member

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    Your Mercedes:
    C220 S203 modified to 175 PS
    Thank you, appreciated. Any thoughts then? There is loads on the interweb about this problem but no consistent set of causes. Pretty sure it's not the Cat!
     
  4. television

    television Always remembered RIP

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    Your Mercedes:
    2002 SL500, 216 CL500, all fully loaded
    Sadly I am not a diesel man, and hopefully someone will answer you problem
     
  5. turbopete

    turbopete Senior Member

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    Spennymoor
    Your Mercedes:
    2010 '60' Ford Mondeo 2.0TDCi Zetec (sorry)
    MAF? does the car rev as expected but not move, or does it just not do anything until it sets off? Auto's arent really my thing, but it could be in need of a transmission fluid change or similar
     
  6. Cole@MBS

    Cole@MBS Forum Supporter Authorised Forum Supporter

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    Your Mercedes:
    124 300 CE 24 Coupe, 209 240 CLK
    There is a vacuum system on the 203, its pulled from the brake booster, it controls the egr and turbo, as well as headlights and rear head rest droppers, a simple brake anywhere in this system cause a major fault and be logging fault codes and putting the engine light on.....
     
  7. OP
    Slacky28

    Slacky28 New Member

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    Your Mercedes:
    C220 S203 modified to 175 PS
    Thank you all - apologies

    Sorry all above and belated thankyou - I was not picking up any post notices after first from Television. Possibly updated spam software.

    In answer to some... I have cleaned out the EGR, the Gearbox Fluid and Filter, and had a +31 BhP remap from Black Code :) (+ figure theirs, dyno'd from same age/model car; and I believe them).

    V pleased with results of all. Black Code remap replaced a Commonrail booster plug-in which cost more but was inferior by far to the proper remap (cos it now feels like a natural car, not a boosted one, even tho results are actually better).

    But STILL this bl@@dy "Oh, he has pressed the accelerator, let's translate that into German and tell the ECU" to, er, GO (schnell bitte, errrr, please.... there's a lorry coming round the roundabout!) problem from standstill.

    Black Code think it's a problem with the Pedal Value Sensor. The guy who looked after it for previous owner said Vacuum. Local MB dealer patronisingly disparaged forums and said he doubted there was a problem at all (because his senior tech drove it to fix an earlier problem and never mentioned it).

    Unhappy, confused and basically... I love this car except it makes me panic at roundabouts and T Junctions. I don't want it to be a 911 (been there). I just want it to go... reasonably smartly, when I ask it to.

    Slacky
     
  8. OP
    Slacky28

    Slacky28 New Member

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    Your Mercedes:
    C220 S203 modified to 175 PS
    ps... it's not gearbox, the engine revs fine with no restrictions (apart from engine breaking, using the gears helps a bit (I'm using 2 and 3 at "difficult junctions). it accelerates beautifully at kickdown for overtaking (with a small lag still). There is no symptom other than "having a little conversation with itself" before obeying what the throttle is mechanically telling it to do. The slower the speed, the more pronounced, from standstill... dangerously slow in my opinion!
     
  9. BachelorDays

    BachelorDays Senior Member

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    Your Mercedes:
    2000 w210 E240 91k (Nov13)
    Pedal sensor would be a reason. You could exclude the MAF from all this by disconnecting it and taking it around the block. Does it happen when engine cold as well?
     
  10. DY2

    DY2 Senior Member

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    Your Mercedes:
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  11. Carl@MBS

    Carl@MBS <span style="color: red;">Authorised Forum Support

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    Your Mercedes:
    164 320 AMG & 211 320CDI
    To be fair the diesels don't have an instant response, have you driven others to confirm its worse than normal?
     
  12. oigle

    oigle Senior Member

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    Your Mercedes:
    Currently 2003 ML270. 2012 Nissan Maxima 250SL.
    My 270 motor in my ML had similar issues from new - positively dangerous on roundabouts etc with lack of immediate response. I had my ecu remapped to fix it (and it did). I wonder if your rempap or whatever you had done has not been done well in that area?
    As an aside, people who have deleted the egr from the system have found throttle response to be considerably better afterwards. Worth doing anyway for many other reasons.
     
  13. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    Your Mercedes:
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    A throttle pedla sensor will cause this as well, a leaking vaccum system wouldnt cause hesistation (but would cause lots of other issues as mentiond)
     

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