w140 s320 m104, uneven idle

Discussion in 'Engine' started by satbasi, Dec 16, 2014.

  1. satbasi

    satbasi Active Member

    Messages:
    81
    Joined:
    Jan 13, 2008
    Location:
    Wolves, UK
    Car:
    Mercedes s320 limo business edition
    Hi everyone,

    Just wanted to pick your brains on this one..I purchased a w140 s320 limo business edition in august. Great car, which I purchased from a relative. As the owner has passed away, the car was parked up for about 9 months. When I got the car the engine was running rich, black smoke & heavy petrol smell from exhaust. New ngk sparkplugs sorted this.

    However, whilst it no longer runs rich, the idle is not perfectly smooth. its no uneven really bad - but just a bit uneven when idling. I have cleaned the maf but no difference. Any suggestions please as to what you think it maybe?

    Also gear change can sometimes be a bit rough. The cars has got 120k on the clock, with merc servicing til about 80k, after that a local garage serviced it. I noticed the red tab on the gearbox oil dipstick cover is missing - not sure of oil was changed/looked at, maybe red tab was not replaced.

    Any suggestions on how often & procedure on gearbox oil change?

    Your help is appreciated...:d
     
  2. Borys

    Borys Hardcore MB Enthusiast

    Messages:
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    Feb 16, 2011
    Location:
    Nowe nad Wisla
    Car:
    2005 cl500
    If tab is missing either a level check or service - I'would do routine service on it regardless.
    Anyways I would do spark plugs, filters,oil - basic service and see what happens (coil packs can play up sometimes too) To service gear box is no more then 130 quid from MB for parts and would only use their kit (had w140 before, serviced box at local garage and it blew after 1k miles-wrong oil) They are great cars and I'm sure it will be an easy fix
     
  3. OP
    OP
    satbasi

    satbasi Active Member

    Messages:
    81
    Joined:
    Jan 13, 2008
    Location:
    Wolves, UK
    Car:
    Mercedes s320 limo business edition
    Thanks for your help Borys
     
  4. Borys

    Borys Hardcore MB Enthusiast

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    Just be patience, it will run great
     
  5. Stratman

    Stratman Hardcore MB Enthusiast

    Messages:
    4,129
    Joined:
    Jun 15, 2003
    Location:
    Sunbury
    Car:
    W203 C200 CDI '04Estate
    You don't say what year the car is, but I believe the M104 was one of the engines affected by the wiring loom saga. The insulation on the wires was basically bio degradable, leading to all sorts of problems including rough running.

    Pick a few random connectors on the engine and check the condition of the wiring. The HT plug leads can also be affected.

    Take a look at this thread, although I stress it's only a possibility and not a certainty.

    Hopefully someone with more information will pop in soon.
     
  6. OP
    OP
    satbasi

    satbasi Active Member

    Messages:
    81
    Joined:
    Jan 13, 2008
    Location:
    Wolves, UK
    Car:
    Mercedes s320 limo business edition
    Hi Stratman, the car is a t reg 99 model, was the wiring loom problem on earlier models? I forgot to mention there is also a slight oil leak at the front of engine-near/above the alternator.

    When i changed plugs i saw that the ht lead connector to the plug closer to bulkhead has been repaired/stuck on to wire with some sort of silicone. Looks & feels strong enough but surely thats not normal?
     
  7. Stratman

    Stratman Hardcore MB Enthusiast

    Messages:
    4,129
    Joined:
    Jun 15, 2003
    Location:
    Sunbury
    Car:
    W203 C200 CDI '04Estate
    Some more information

    According to the link above, it's 93-95 that seem to be affected.

    I don't know about the silicone, perhaps it's to stop water getting in?
     

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