If you're idle is erratic AND acceleration off idle poor when warm, I would absolutely check the airflow meter pot before continuing. These potentiometers will eventually wear out the resistance element where they spend the most time - at idle. When that happens, it will fail in it's main function, which is to alert the ECU of a rapid change in airflow. Since the wear is at the idle airflow position, that is where you will notice it.

At idle, this pot will also send erratic info to the ECU, due to poor contact, causing the ECU to vary mixture via the EHA, which causes erratic idle. This does NOT occur with a cold engine because idle speed is higher, and the pot is functioning in a range where contact is still good.

The pot is located on the side of the airflow meter unit, where the pivot shaft of the meter vane is located. It is fastened with two screws through slots, so it can be rotated for calibration. Before removal, it should be marked for position so it or a new one can be installed in the same position, for rough calibration. It can also be rotated slightly to see if that will change the symptom of off-idle hesitation and unstable idle.

Moving the pot will temporarily upset idle speed, but it is not used to determine stable idle speed. It is not available from Mercedes - pity - but can be found at Bosch electronics suppliers. Info available searching posts here.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7