These M103's can be a nitemare to diagnose primarily due to all the different parts the factory threw at the motor.

Some of the coolant temperature sensors have an ohm reading of 3k+ while others have a sub 50 ohm reading, both values are on a cold motor as an example.

Some M103's require removing the valve cover to access the coolant temperature sensor, thankfully mine doesnt... the 22mm socket dropped right on.

Some ECU's or whatever does the adjustment allow for the Idle Air Valve in front of the fuel distributor to raise the idle when disconnected, my M103 on two different units dropped the idle speed by at least 500rpm at startup from cold.

Some EHA's have a 2mm set screw adjustment, others have a flat head screw.

The upshot is the controlling or adjusting the startup idle speed on this motor is greatly lacking in fun.

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1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."