Hi,
Pull the distributor and check for oil on the trigger-points in the distributor base. You can also trace the problem on a scope. The injectors are fired in the following pairs: #1&5, 2&7, 3&6, 4&8. Usually when you see a problem on any of these pairs of cylinders...it's trigger-points.
Regards,
Randy D.


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W.R.Durrance
ASE Master Tech
Mercedes Tech 19 Years