W124 E220 1993 irregular idle, hi revs, returns to normal on restart

Discussion in 'Engine' started by jacodupreez, Oct 10, 2011.

  1. jacodupreez

    jacodupreez New Member

    Messages:
    2
    Joined:
    Oct 10, 2011
    Car:
    93 e220 w124
    Hi,

    just bought a 1993 E220 W124, and in the last week it has been giving me a bit of a head ache.
    it would for no reason start shuddering, as if its not firing on one cylinder, but if the car is switched of and restarted, it runs normal.
    Revs also pick up to 1500 rpm.
    have changed the spark plugs today, as i thought one might be faulty . ( disconnected each plug lead while it was in its "shuddering state" ) and found one to be "dead" cylinder no 2

    But the problem returned a couple of hours later. this time on cylinder 1 and then on cylinder 4.

    What really confuses me is that, once the car is restarted, it returnes to normal, for a time.... have noticed that if sudden braking / stopping is done it also "misfires"
     
  2. grober

    grober MB Master

    Messages:
    27,943
    Joined:
    Jun 22, 2003
    Location:
    Perth, Scotland
    Car:
    W204 C200CDI Estate
    Sounds as if you might have a problem with the OVP relay. quite common -they can often be repaired by resoldering the connections on the relay small internal circuit board. Try cleaning up the throttle body throat with solvent also- they get dirty and this effects idling. try doing a search on here for details.
     
  3. OP
    OP
    jacodupreez

    jacodupreez New Member

    Messages:
    2
    Joined:
    Oct 10, 2011
    Car:
    93 e220 w124
    thanx grober, will clean the throttle body today, because i noticed something else this morning, when ever it does it "misfiring / shuttering " thing and i floor the accelerator, causing the car to drop a gear or 2, pick up revs, problem solved... for a bit.

    checked the relay fuse, its fine, plus when i disconnected the fuse, i could hear a reaction.
     
  4. Vlad

    Vlad MB Enthusiast

    Messages:
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    May 30, 2003
    Location:
    Reading, England
    Car:
    Various Mercs come and go
    The OVP relay may have an OK fuse, but internally the soldering starts to break down casuing erratic faults. Very common and the new OVP relays have a slight redesign. I personally would take the plunge and buy a new one.
     
  5. balge

    balge Active Member

    Messages:
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    Joined:
    Jul 28, 2010
    Location:
    Central England
    Car:
    Mercedes-Benz W124
  6. neilz

    neilz MB Enthusiast

    Messages:
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    Joined:
    Nov 14, 2009
    Location:
    London
    Car:
    W140 S320L, 1997, Black with Black Bird's Eye Maple trim
    I could be completely wrong so don't take my word for it, but I had this exact problem on my W124 E220 from '95 (which I've just sold) and it just needed new HT leads and ignition coils.
     
    Last edited: Oct 11, 2011

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