Nuebie,

Before you go screwing with the carbs make sure your ignition system is working perfectly as these two items are closely linked diagnostically.

Your ignition trouble sounds to me like a bad condenser. This can cause periodic weak spark as well as backfiring. Also, you mention that it runs fine for a few minutes then dies, this is very typical of a condenser failure. The condenser (for non-transistorized ignitions) is the little cylinder screwed to the side of the distributor, these are cheap <$10.

The carbeurator trouble for your car is infamous. The weights/flaps on the exhaust manifold riser get stuck open heating the carb excessively eventually warping the carb top plate and body. Tightening the screws in this case tends to make things worse. Carb needs rebuild where the flatness of the mating surfaces is checked.

Good luck!

__________________
Kyle Fitzpatrick
Materials Engineer

1969 300SEL 6.3
1992 300E
1994 E320 Touring