Rough idle or stalling in D or R.
I have the same problem as described in this threat. I drive a 1993 280E euro without the EGR. When starting cold she will drive fine and fast. The minute she is on operating temp the idle will be very low when coming to a halt and if I donīt put here in N or P she will die on me. The engine will slowly drop in rpmīs and then start to shake as if she is running on only a few cylinders. I have replaced the OVP, fuel pump relay, all cables, sparkplugs and the boots under the coils and, this morning, the air mass meter. It didnīt do didly squat. The problem is still there. I had the Benz dealer read the codes and they told me that the air mass meter was faulty and that is why I replaced it. I agree that it does sound like a relay or a sensor since as soon as I step on the throttle the car runs really smooth and fine. She will only act up on idle. I have an after market cruise built in. This one lets me pull the gas so the engine is out of its idle position at a stand still and the idle is slightly higher then it should be. This seems to work but is a temp measure untill i fix the problem.
I hope that this threat brings an answre so I can be a happy benz driver again.
I will talk to my benz dealer again tomorrow and return his beautifull air mass sensor.
Thanks and happy motoring,