Exactly the experience with my car. First had to ensure that the AAV was closing completely at less than 70ºC, then turn the idle air screw down until the surging while cold stops, which was around 1500 rpm. Results in warm idle around 900 rpm warm (in P or N).

Deaconblues,

Your idle screw could probably even be turned down lower. My 350 is perfectly happy with a cold idle of no more than 1000rpm and a hot idle around 600. Only on the hottest Sydney days (35 degrees C plus) is the hot idle likely to get a bit too low (500rpm or even less).

Greg

__________________
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.

Greg-

Are you citing idle speed while in gear or in neutral (park)?

The current setting results in a smooth warm idle of ~500 when in gear, so I think the idle screw is in a good place. Is the cold idle of 1500 too high? I could lower it more by further inserting the cylinder of the AAV (didn't have to fully insert it to get it to close completely at temp after the rebuild) which would reduce the added cold idle air and the temperature for closure. Good to share common experiences!

BTW, Steve helped me to achieve stable hot idle by suggesting a series resistor to the coolant temp sensor for the ECU. Used to get so lean after heatsoaking that it would die while in gear at stoplights.

You seem to have a big difference between idle in park or neutral (900) and in gear (500). I'm no longer using my 350 as a daily driver, but from memory, hot idle in "P" or "N" is around 750 and in "D" around 600.

__________________
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.