My '87 260E has always been a somewhat reluctant starter and needed to warm up for a minute before it would "take the throttle" with any enthusiasm. I attributed that to age & 200,000 plus miles. Something to live with. Replacing half a dozen rubber bits and a couple of hard vacuum line helped lots, but not completely.
Then I got a copy of Stu Ritter's book, "MB E-class owner's bible". It's got some good reading. It's more of a "how things work" than a "fix it like this" book. I stumbled across a paragraph on M103 drivability & the problems described fit me to a T. There is an adjustment to the electro-hydraulic actuator (EHA) that hangs off the back side of the fuel distributor. This is the gizmo that takes the commands from the ECU and adjusts the fuel distributor pressure. It's the "muscle" for the ECU's "brains".
Anyway, pull the air cleaner box, the connector and, two screws later, the EHA is in my hand. There are two small O-rings that stayed on the side of the fuel distributor. Gas does squirt out when loosening the screws, but only a few drops. It would smart to get it in the eyes. On the side of the EHA that faces the dist, there is a brass screw with a straight slot. This is just a cover. Unscrew it about ten turns (very, very fine threads) and underneath is a brass setscrew with a 2mm internal hex. 1/4 turn clockwise, and reassemble all "in reverse order" as they say.
The difference was immediately apparent on my somewhat cooled off engine. About two hours since driven. Fired up quicker & idled smoother. The acid test will be tomorrow AM when the engine is completely cold. Well, cold for NJ in September.
Stu says this isn't really making the engine run richer, it's only making up for normal wear & tear. Bringing it back to the original spec's, as it were. OK!
Smooth,