Cold Advance Solenoid Valve

Distributor Vacuum Advance System:

The distributor vacuum advance is A dual diaphragm type, having a main vacuum chamber and a sub-vacuum chamber. To augment the ignition timing during cold start and warm-up conditions, the ECU utilizes the Sub-Vacuum Chamber (controlled by the cold advance solenoid valve). When the engine coolant temperature is below 50°C (122°F) the ECU energizes the cold advance solenoid valve. By this action, the intake manifold vacuum is no longer vented to atmosphere and instead is applied to the sub-vacuum chamber. As a result, the timing is advanced an additional 5° (in crank angle) to whatever advance is being applied by the main vacuum chamber. During warm-up when the engine coolant temperature exceeds 50°C (122°F), the ECU de-energizes the cold advance control solenoid valve. As a result, the intake manifold vacuum is vented to atmosphere, preventing the additional timing advance. Although the cold advance solenoid valves source is common to the distributor advance solenoid valve, it has a one way check valve to prevent its operation from affecting the distributor advance solenoid valve.