On the M103 it's under the air filter housing -- three nuts on rubber mounts. Idel control valve is held down by a strap -- silver can with a single two wire connector and two large rubber hoses.

Unplug, unclamp, and work the hoses off. If the hoses are really hard, you should consider replacing them. Wash valve out with carb or brake parts cleaner until the solvent rund out clean, and re-install.

I'm not sure where the valve is on the M104 (twin cam).

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!