I'm guessing that you have a misfire. Does this only happen at 2000 or at any steady throttle position? Can you duplicate it out of gear with the engine held at a steady speed say 2000?

Being a 1996 I presume you have Motronic engine control, which means coil on plug rather than distributors. I would guess the problem could be a coil to plug connector. Unfortunately it could be all manner of things though.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician