I too have a '95 E300 Diesel.

My throttle linkage was stiff when I first got the car. When I changed the oil the first time I popped off each of the ball and socket joints on the throttle linkage and sprayed with PB blaster or WD40 - then reassembled. This helped quite a bit to loosen up the linkage and reduce the pedal effort required to increase throttle opening.

I didn't have the sticking you describe - that tells me that perhaps your return spring has broken?

cleaning and lubricating all the joints in the system, and perhaps applying some Napa cable lube to the cable would also be a good idea - that stuff has worked magic for me on some push pull cables on equipment.

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95 E300 Diesel 265k and counting