Civic 1300

The engine coolant thermosensor energizes the ignition solenoid valve when coolant temperature is below 167° F. Manifold vacuum is allowed through the valve to control vacuum advance. When the engine warms up, the solenoid is de-energized and there is no vacuum advance.

Fig 1: Civic 1300 Ignition Timing Controls

Courtesy of AMERICAN HONDA MOTOR CO., INC.