Air Injection: Description and Operation

Purpose

This system is used to direct air into the exhaust ports or catalytic converter to extend the combustion of unburned hydrocarbons (HC) and carbon monoxide (CO) in exhaust system. This air is also used as the oxygen source for the catalytic converter.




Pickup & 4Runner, Exc. California

Air flow on these models is controlled by a valve assembly that includes a vacuum operated shut-off valve and a reed valve. During normal operation, the shut-off valve is held open by manifold vacuum, vacuum created by exhaust pulses opens the reed valve and air is drawn into the exhaust stream. Manifold vacuum is supplied to the shut-off valve through a dual diaphragm Vacuum Control Valve (VCV), which allows vacuum to be transmitted as long as vacuum strength in the two diaphragm chambers remains equal. Under high vacuum conditions, such as during deceleration, vacuum in the lower diaphragm chamber increases, the VCV control valve vents the shut-off valve operating vacuum to atmosphere and air injection is momentarily interrupted until vacuum is equalized in the two diaphragm chambers. On 1985---88 models, a Vacuum Transmitting Valve (VTV) is used to delay closing of the shutoff valve.




Pickup & 4Runner, California

On these models, the air suction and fuel system feedback control systems are used in conjunction with one another. Air is drawn into the exhaust stream through an EACV and a reed valve. The EACV is closed when coolant temperature is below 43°F at any engine speed and when coolant temperature is above 131°F with engine speed above 1390 RPM. Under all other operating conditions, the EACV is open and the air suction system operates normally.