I have a 1993 E280

I've noticed over the recent months, the rpm fluctuates from 300 to 1200 while idling especially when I have just driven for a short distance after a cold start. The Mercedes agent have hooked up a laptop computer diagnostic to check the problem but found nothing.

Just 2 days ago I notice that from a standstill at the traffic light, if I step hard on the accelerator to drive off, the car seems to stall, hesitate for while, and then move off. Another mechanic checked the fuel pump and found nothing either.

Then the car really started stalling, especially if I start the car from stand still. I almost had to tow the car back. But after revving the engine gentling (to prevent stalling) for a while, and driving slowly for a while the problem seems to resolve.

What is the problem ? Can a faulty alternator cause this ?