[W126 Coupe] idle recurring "cough"

[Mister McGoo]

You say you keep cleaning the rotor and changing the rotor and cap... you have not mentioned the ignition wires or plugs which form the balance of the physical ignition system.  Have you changed those?  Are they OEM spec components?  
 
Distributor "out of balance"?  In my experience, shouldn't have any distributor problems, particularly at only 100,000 mi.    -Bellamy
 


Date: Fri, 19 Nov 2010 12:20:15 -0500
From: J.Hirsch at mac.com
To: mbcoupes at mbcoupes.com
Subject: [W126 Coupe] idle recurring "cough"

On going minor problem since Sept 1


Car has  Bosch  rotor and distributor cap



Bosch factory  rotors.... made in Germany and Spain




This is what I did on Sept 2:


["Rotor was slightly burnt on one side, discolored, darker than rest of copper edge which is “normal.” But what is normal?
Showed it to a friend who is a very good auto mechanic.
     He said it looks  “a little more burnt than usual.” Told me to sand down that edge  to get the corrosion off
Put back dist. cap and with cleaned up rotor, car runs great, at idle and highway
Got new Bosch cap and rotor and will install later today]



One copper end of the rotor gets discolored...slighty burned or corroded.
Filed down  copper with 600 grit emory cloth.  Put back and all is fine, which I have done several times before which makes me think distributor is "out of balance


Factory coil and ignition  module.  Car has neve been "fooled with"



Have used my 1990  560 SEC  for a total of maybe 600 miles since Sept 3.  Changed   rotor  and  dist cap at this time.
Car ran great...again


Went  about 250 miles  after Sept 3 when car started "coughing" at idle
Oct 4, changed spark plugs and rotor at this time, early   and car ran smooth..again


Have gone about 300 miles  since October., yesterday car started "coughing" at idle and not  running too smooth at speed also
Took out  rotor earlier today, installed new  rotor,  and  "presto" car is smooth and quick again.


Do you think  the distributor is out of balance and time for replacement?  car  just tuned 100,000 miles


or is there something else that is Mercedes related i am not aware of?  i  think it is just basic  "car problem," dist. getting tired.


Jay H


Had  the same  thing happen on two "gringo" cars of mine several years ago...1973 Eldorado and 1963 Lincoln out of balance distributors
They were "eating points"  when cars had points.  1973 was  last year for points on  Caddy's
Would change points, good for  a several  hundred miles and then "coughing and wheezing"


Changed distributors and no more problems
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