There is never a reason to adjust the idle screw on a fuel-injected E30. Idle should never be mechanically adjusted using this screw or the AFM idle bypass screw. The Motronic ECU electronically controls the idle via the Idle Control Valve (ICV).

The idle screw only opens the throttle plate by about the thickness of a human hair to ensure the plate doesn’t bind with the throttle body bore.

In the rare case that a previous owner has adjusted it and you need to reset it, here are the factory instructions:

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