280 Models
The system is designed to inject air into the exhaust ports during a specified period of engine warm-up operation. The oxygen sensor detects the additional oxygen in the exhaust and richens the air/fuel mixture slightly, resulting in smooth operation.
When coolant is below 62°F (17°C), the first thermal valve is closed and no vacuum reaches the diverter valve. Air is vented to atmosphere. When the first valve opens, vacuum passes through to open the diverter valve and direct air to the cylinder head. When the second thermal valve opens at 122°F (50°C), the vacuum is bled to atmosphere at the air intake. The diverter valve once again vents air pressure.