The 1997 E420 is a great car! However the throttle actuator has been known to cause quite a few problems, I'll bet you that "it" is causing the problems. Since the car has an electronic accelerator that controls all throttle functions the Benz dealer should look for the problem there.

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS M.B. TECH