The EDS (Electronic Diesel System,A.K.A. Engine CPU) in the Originally equipped
OM603.XXX chassis Controlled the Idle.

I suppose you could get an EDS unit from a 603 Donor and wire it up with all
the necessary inputs to run your idle...An awful lot of work,and Uncharted
Waters.

The OM603 I.P. idle can be set Mechanically with the bolt (With locking Nut)
that's above the Electronic Actuator on the back of the I.P.

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'84 300SD sold
124.128