1999 Other Mercedes Benz Models SMOKES AND UP/DOWN IDLING

Sounds like it is misfiring. Does it smell like fuel under the hood or out the tail pipe? You need to check for a fuel leak so the car doesnt catch fire, beyond that when was the last tune up? Is the"check engine L:ight " on? Have the PCM (computer) scanned for codes. If the PCM sees a problem it will store a code that will help in diagnosing the problem, get back with the exact codes