My high mileage 71 220D surges at idle when cold (idles fast then slow) & will smooth out when warm but the surge will carry to a higher rpm once warm. (about 1400 rpm) There is no surge once the motor is under a loaded condition. Has anyone experienced this or have any ideas as to what it could be? The car runs fine otherwise, not the fastest thing in the world but guaranteed to get you there. Gas mileage is 24mpg. I've cleaned/adjusted throttle cable, linkage, intake & choke all to no avail. Any help is appreciated, Thanks.