[W126 Coupe] idles rough when properly lean

[Dick Spellman]

Hello Richard:

To help narrow the possibilities, try answering these questions one by one.

What is the mileage on the MB?

How many miles since the following were replaced? (electrics)
ignition wires
O2 sensor
sparky plugs
cap and rotor
In other words, are the 'electrics' in good condition and how many miles
have transpired since each was replaced?

Have you checked for a 'fat' spark on the coil wire?
Have you checked for a 'fat' spark on each of the plug wires?
Do you need to know how to do this???

How many miles since the following were replaced? (fuel)
injectors
fuel filter
accumulator
Any major work been done on the fuel system like replacement of fuel
distributor, other stuff?  Describe and how many miles since R&R?
Does the fuel pump deliver the needed pressure?
What is the pressure?
Does the fuel pump make any noise at idle or hum on cold days, has it ever
been replaced?
Do you smell any gas fumes around the fuel distributor and are there any
signs of fuel (wet area) in and around the EHA valve?

Are you running this engine on Premium only?
Or are you occasionally or always dropping the fuel grade and what grade to
you use?
Have you dumped one can of BG-44 in the fuel tank with the prescribed
Premium and volume of gas and given the injection system a good gutting of
the crud build-up?

I think we would all be interested in your reply to help us narrow this
issue down.

Dick