I have a 1983 500se euro spec 180 000 miles.
I use this car for business and drive regularly acroos Europe.It is wonderfull!!

However,recently in order to prevent the engine stalling when it is put into drive the idle has had to be adjusted to run at about 1100 RPM when in park or neutral.
In drive the car then idles (at correct running temp.)at about 550RPM.
If the Air-Con is switched on the engine will stall at standstill in drive.

I have replaced ignition leads,distributer cap,rotor arm,plugs,air filter and although the engine now runs much smoother this problem has NOT gone away.

Also since this problem arose the car does not idle well and will sometimes shake and judder slightly in gear particularly when warm.

There is no oil useage and oil pressure is good.

Any help would be appreciated as this is spoiling an otherwise wonderfull car.

Thanks in advance.