Sounds like the control rod travel sensor. I don't think it's adjustable so any play is either a failure or inconsequential. Some help, huh?

From what I can tell, it's a load input to the EDS system that controls emissions devices and the charge pressure device. The EDS also sends a signal to the ELR which controls idle. I think the EDS only sends an RPM signal to the ELR.

Sixto
91 300SE
87 300SDL
83 300SD