my car is a 1986 230E (mannual trans) and although my idle problem may not be described as rough, i certainly know that something is wrong with it since I heard from another post that your idle should always stay as is except during start-up when it goes up a bit to about 10-11 then immediately goes down to about 8-9. My M102 engine idles generally fine, does the start-up idle and normally does not move and inch (except of course when revving). However when the airconditioning system cuts in (compressor and aux fun running) my idle goes down to about 5-6 (engines vibrates almost to a point of stopping) then returns to 8-9 and stays there even when it cuts off. My technician has diagnosed, adjusted/checked a lot of things and finally told me that based on his expereince in repairing MBs, the M102 engine is normally like that being smaller than it's brothers (M103 and M104). I really trust him with a lot of things about my car but no one is perfect and i hope he's wrong about this one.

I know i have an adjustable idle control valve which i replaced last September 2002 due to rough and constantly high idle. Could this be the culprit? Can I just adjust it so that it can better compensate whenever the aircon cuts in?

Added input: My airconditioning system is not an original MB due to our tropical climate. It has been converted and is using a japanese system and it remained satisfactory so far in terms of output compared to the original which is cold but not as cold.

Really need your help on this one.