I've posted my high idle problem on my 380sel earlier.
I had replaced many parts as suggested by the members here.
I've replaced idle speed control unit 002 545 40 32. I've replaced idle speed actuator 000 141 14 25. My mechanics ( 2 different one) has checked almost all - throttles, cables etc etc.
Still my idle speed is sitting on 1300 rpm. I'm afraid my transmission will be wrecked soon as the car jerk in between gear shift due to the high idle.
One mechanic even suggested I convert my whole idle system to a manual adjustable version bypassing the electronic control system. I understand Mercedes made different version for different countries.
Should I go ahead with this or is any kind people here be able to help me if you have similar experience.
My engine is 116 962 version (Hong Kong). I'm residing in Australia now. The Australian idle speed version operates on the manual one.

Have you tried taking it to the dealership? Maybe they would be able to diagnose your problem accurately. Good luck...

Did your mechanics check your throttle switch. Some of the world models had a vacuum switch on the left fender to gauge the idle position. Most other models had a switch on the throttle shaft. If this switch is open the car will idle high.

I would also test for vacuum leaks. I would also test the idle valve to see what its doing. The early systems could close the valve down with a 70/30 duty cycle. This means that the valve is pulsed with a steady frequency (say 100hz - 100 times a second). The pulsewidth is then 1/100 of a second. For this period the coil can be energized 70% of the time and off 30% of the time. This is as far as the system can energize the valve. The opposite to this would be holding the circuit for 30% and off 70%. All proper idle correction lies in between. So... one must measure this to know whether the system is trying to do its job. If the system has the valve energized 70/30 then there is either too much air entering from other sources or the valve isn't being closed by the strong signal.

To verify whether all the air is coming through the valve the passage can be blocked; the engine should die.

I would also be sure your timing isn't too high.

have your overvoltage relay re-checked.
corrected my similar problem before.

high idle speed
 

try unplugging the leads from the idle speed valve to see it it is working at all. It should speed up. One thing that will cause high idle speed is a failed temperature sensor--though this will usually bring the RPM up to 1000 or so. Air leaks (cracks)in the rubber 'housing' on the bottom of the air flow plate will also cause this problem, though usually 'leans out' the mixture too much unless you have O2 sensor system.

I like to thank everyone for their very kind feedback to my problem.
I just notice that my idle speed is sitting under 1000rpm just now! Used to be around 1300rpm yesterday until I replaced another idle control actuator again(valve).
This time, the idle speed will suddenly rush up to 1500rpm when I shift from D to N and then settle back under 1000rpm after about 5 seconds.
This always happen between shifting only.
Could this be due to some other new problem now?
Will this sudden surge of power between shifting damaged my transmission?
Thank you all once again!