wdawson61, ould be nice to know what kind of 126 you have (year/model).

There's a switch at the far end of throttle pedal travel. Remove the switch and see if things improve.

300SDs have a cable that comes up the passenger side of the engine to a system of bell cranks on the valve cover. The cable ends in a rubber accordion section and a ball socket. Check that there is a little bit of slack in this cable when the throttle pedal is in the idle position. 300SDLs, 350SDs and 350SDLs have this cable come up by the oil filter. Same check.

Sixto
87 300D