[androver]

The idle speed has begun to vary on my 1994 220 Sli (nasp). In the past it's been consistent around 900 rpm. Recently, after fully warming up it's sometimes around 1500 rpm then may drop back a bit, sometimes to just below 1000. Sometimes when sitting in traffic increases by a few hundred revs, sometimes varying. Any ideas? Temp on gauge is normal.
Andrew

[RoverRevival]

air pipe leak would be my first point of call
reset your stepper motor (ignition on, pump accelerator 5 times)

[E_T_V]

Reset the stepper motor as above.

If that doesn't help then when the revs are high and the engine at normal operating temp, check to see if the coolant fan is running. If the coolant fans are running all the time then it is probably either a faulty coolant temp sensor (very common) or the wiring for it - often the plug breaks)

Replacement of either is straightforward.