Yeah the good old M137. Anyone who's been around MB's for awhile understands why this engine didn't hang around too long. The CSO feature (cylinder shut-off) wasn't a bad idea, it just had some unintended consequences.

For those who don't know how it works, here it is. Under certain driving conditions, the left bank of cylinders was shut down to improve fuel economy. The resulting temperature and pressure change caused some blow-by, eventually putting enough engine oil into the intake manifold to start fouling the spark plugs. Believe it or not, a slight mis-fire on the M137 is almost undetectable to the driver. Because of this, the situation would gradually worsen, resulting in damage to the ignition coils.

The fix is pretty straight-forward. Replace the plugs, coils, and insulating boots. Then, remove the intake manifold and clean out all the oil to prevent a re-occurrence of the plug fouling. When this is done, drive the car to a shop equipped with SDS. With SDS, the sensitivity for mis-fire detection can be decreased by means of a software update, resulting in fewer "false alarms". Lastly, use SDS to disable the CSO feature (after all, CSO started the whole mess to begin with).

There are a few other scenarios, but back in the day, this was the most common. Since then, the ignition coils have been improved. In fact, I rarely see the newer version cause any problems.