IDLE SPEED ADJUSTMENT
 

Can someone post an illustration of the location of the IDLE ADJUSTMENT SCREW/KNOB on a MB 420SEL/560SEL V8 motor? NOT THE CO adjustment of the fuel distributor but the screw to increase or decrease idle speed WITHOUT touching the fuel distributor CO adjustment.

I'm almost 100% certain it's electrically controlled. I just posted a thread regarding idle diagnosis in these engines; check it out and see if any fit your symptoms! Anything other than just high idling?

-Carlen

^ What he said. There is a box that can fail on some models that will cause high idle, etc.

I could not even begin to guess where a manual adjustment would be. Adjusting the AF ratio does not change idle anyway.

There is no manual adjustment, it is computer controlled with the idle control valve.

WTB WUR
 

Also looking for a used and functioning Warm Up Regulator for no emissions gear Gen 1 Euro 500SEL Bosch part No. 0488 140 056 B 916 or MB part No. 116 700 362

No high idle or erratic idle; just low idle enough to want to stall car sometimes; recall seen a pic from a 126 manual showing a mechanical idle screw hidden somewhere low in the intake manifold?

I know there's a screw for the M103, and I think in earlier iterations of the M117 there was a screw on the warm up regulator, which was kicked once we went to electronic idle control... As to late M116/7, no such screw exists...

I think you might be the first to have a low idle problem :D

Idle on my 500sec was low - ~500rpm - so I adjusted the throttle cable adjuster ( up to ~750-800) as a temp until I can look into it "someday". Mine is a euro so I don't know if others had this cable adjustment. It's a plastic threaded piece with nut near the end of the cable under the hood.