2000 W210 E320 Cdi Auto Estate (100K miles): Reduced Performance: MAF? Pressure Gate?

Discussion in 'Engine' started by gwiseman, Aug 4, 2011.

  1. gwiseman

    gwiseman New Member

    Messages:
    9
    Joined:
    Mar 10, 2006
    Location:
    London
    Car:
    CLK55 209 Convertible
    Hi all,

    After extensive lurking and learning, my first post:

    Day 1: Car starts and idles as normal but shudders as I'm pulling off, as if it's trying to pull in third (winter mode and handbrake not engaged!). After just a few metres, the car drives fine, but shudders again when I next pull away from rest. Drive around the block and park up.

    Read about a 'this might fix things' suggestion (ignition on, engine off, hold kickdown for 15 seconds, wait 2 minutes, switch all off). I try this and the shuddering does indeed seems to have disappeared. Don't know if this is a fluke and don't have time for a spin.

    On Day 2, the car starts and idles as normal, but on pulling away it stalls. Tried again and did 100 mile round trip with no problem starting from rest, however engine responsiveness/performance is not right - the car doesn't seem to want to rev past 2000rpm, even with a heavy foot. I have all gears - it's not in limp home mode I don't think as it still picks up speed OK, and can cruise at 70, but not free-revving and not wanting to accelerate as quickly as normal, seems loathe to spin faster than around 2000 rpm.

    If this sounds like a simple MAF sensor issue, I'm inclined to give it a go and replace myself without paying for a STAR diagnostic. If it's likely to be something else, I probably won't go there... any suggestions?
     
  2. OP
    OP
    gwiseman

    gwiseman New Member

    Messages:
    9
    Joined:
    Mar 10, 2006
    Location:
    London
    Car:
    CLK55 209 Convertible
    A bit more info

    Day 3: Car is driving smooth as normal, just no willingness to rev freely despite accelerator position. Kind of feels like the turbo isn't kicking in? Cruising at 70 is no problem, temperature up to about 70 degrees after 15 minutes.

    I had space on the road to try and kickdown today and hey presto nothing happens when pedal depressed fully... the car picks up a little speed but it's sluggish. Then it displayed 'an EL Power Control'/EPC fault...

    I am thinking throttle sensor now. Could it be?
     
  3. BlackC55

    BlackC55 Authorised Forum Sponsor Authorised Forum Sponsor

    Messages:
    18,741
    Joined:
    Feb 8, 2007
    Location:
    Horndean, Portsmouth, Hampshire, Southsea
    Car:
    C43 AMG with a 55 engine and supercharger, E55 AMG, S500, etc
    Get it plugged in. It will save you time and money.
     
  4. OP
    OP
    gwiseman

    gwiseman New Member

    Messages:
    9
    Joined:
    Mar 10, 2006
    Location:
    London
    Car:
    CLK55 209 Convertible
    Olly, approx how much do you charge to hook a car up to STAR? You are near Peppa Pig World, right ;-)
     
  5. OP
    OP
    gwiseman

    gwiseman New Member

    Messages:
    9
    Joined:
    Mar 10, 2006
    Location:
    London
    Car:
    CLK55 209 Convertible
    Actually, I think I just found out the MAF sensor is shot. Pulled the plastic engine cover and tested pin 5 of the MAF wrt earth: 0.02V at idle and 0.04V when throttle blipped (should be 2V and 4.5V at 5000rpm I believe). I'll stick a new one on in the AM.
     
  6. OP
    OP
    gwiseman

    gwiseman New Member

    Messages:
    9
    Joined:
    Mar 10, 2006
    Location:
    London
    Car:
    CLK55 209 Convertible
    Sorted. I found the best way to easily tap pin 5 to measure the changing signal voltage from the sensor (which is incidentally marked on the cable connector housing and was the end wire, closest to the bumper) was by inserting a needle into the socket of pin 5 where it provides a reliable contact.

    Part was £70 from Merc dealer inc VAT, no discount. Same component is £8 less at eurocarparts - get the Pierburg branded one.

    To fit, remove decorative plastic engine cover with torx driver, only takes a minute. Unscrew two torx-head screws holding sensor in the MAF housing (air filter just needs to be wiggled a bit to reach the lower MAF sensor screw). The old sensor can be slid out -with a twist/wiggle - and the new one slid in with the same motion. Reconnect the cable (it only goes one way) and you can double-check voltage (mine was now 2V at idle and rose as the throttle was blipped). Screw back plastic engine cover.

    Very quick and easy fix (3 mins if you know what you're doing, I took 15 as I've never taken the engine covers off and wanted to check drawings of where the MAF was, check forum posts, confirm voltage properly etc.)

    Turbo now kicks in, engine revs freely, car accelerates as normal, kickdown seems to respond without error code. Fantastic.
     

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