Charlie,

Try the simple test outlined below to take the ELR (Idle Control Actuator) OUT of the loop.
If unplugging the ELR device makes no difference ,chances are it's the "Boogieman".
[Unplugging a functioning ELR should cause a drop
in RPMs.]

"The dreaded EDS (Electronic Diesel System)
[one of the computers behind the Battery] controls the Idle speed."
Through the ELR actuator.


"The classic test of the ELR
(That's the device on the very back side of the Injection Pump,with the wires you've already traced)
is to unplug the two wire connector(with the engine warm and running) and see if the idle changes."

Second test ,With a Warm engine idling turn on the A/C ,Does the ELR
"Pick Up" the dropped RPMs caused by the A/C load? If not another nail
in the ELR 's coffin.

Other tests available on FSM (Factory Service Manual) [OR "CZ" FSM in this case]

If something is awry with the EDS computer[Unusual],I do not think there's any "Fixing" them.'Just replace...(ReCycler's)

Perusing the FSM for a few , Back soon

__________________
'84 300SD sold
124.128