Where is the idle adjust knob on a 1990 124 602

[RichMason]

I've searched all over the forums and internet looking for a picture that will show me the location of the idle adjusting knob on my 1990 124 300D but no luck. Can someone here please point me in the right direction, preferably with a picture? I can't find anything resembling the descriptions and locations on later cars referenced in the forums on my car.

Many thanks!

[sasquatchgeoff]

see drawing of your injection pump (red arrow)

[sixto]

Why do you want to adjust idle? There's a computer that takes care of idle.

Sixto
87 300D

[RichMason]

So it i not on the firewall like the later cars (the 7 position knob)...many thanks!

[sixto]

The firewall trim knob is a feature of middle year cars. Not before 86 and at least for 124s, 126s and 140s not since 90.

Sixto
87 300D

[RichMason]

The idle is too low and not very smooth, even though the ELR is working correctly. If I increase it a touch with the accelerator, it smoothes out. I realize it could be other things but its firing on all cylinders and nothing is pinging. It also drops too low before it recovers. Is the base threshold properly set through the procedure in the FSM or should the ELR settings take care of that as well?

[sixto]

By ELR is working correctly you mean idle drops further if you disconnect the actuator at the tail end of the IP?

The FSM gives specs for idle with and without ELR but IIRC base idle is set with ELR disconnected. I suppose base idle could be off but I don't hear much of folks having to adjust base idle even in cars with 300K miles. You could bump up base idle to where it works for you but it would be nice to have an external tach to note before and after rpms. Maybe take an AC voltage reading of the flywheel sensor.

Does idle improve when the engine is at operating temperature?

Sixto
87 300D

[RichMason]

I backed out the screw 1 turn or so, which smoothed everything out. Plus, it no longer drops below 500 before recovering. I should also clarify that I did the pressure controlled wastegate mod, deleted the EGR and all the valves, and resealed the DVs in the past few weeks. While I saw no indication of this elsewhere, it seems that there may be some input to the ELR that is changed as a result of these other modifications.

Before adjusting, idle was between 500 and 1000 on the gauge, I would estimate 650 to 700. It now still reads well below 1000, 800 or so I would guess. It goes into gear smoothly and doesn't require any extra effort at a stop sign.

Unplugging the ELR produced a notable reduction in idle speed. Warming up the engine made no difference in the idle before adjustment.

Many thanks again.

[sixto]

Cool beans. Can't argue with what is cost to fix

Sixto
87 300D

[pawoSD]

I had to do that on my 617 too....it was shaking, so I brought the idle up from 550 to 700-750ish, tweaked the rack damper, and now its smoooooth. No shake or anything at all.