See Figures 1, 2, 3 and 4
The air induction system is used to send fresh secondary air to the exhaust manifold. During normal engine operation, the exhaust pressure usually pulsates in response to the opening and closing of the exhaust valves. By utilizing the vacuum created by the exhaust pulsation, secondary air can be drawn into the exhaust manifold, in proportion with the vacuum supply. The additional air helps complete the combustion of unburned emissions in the exhaust manifold, thereby reducing CO and HC emissions. The secondary air also increases the efficiency of the TWC converter, further reducing emissions.
The system consists of an air induction valve assembly, a filter, hoses and the connecting tubes. The induction valves contain either one or two reed valve assemblies. The reed valves prevent exhaust from flowing back through the system, into the air cleaner. Some early systems use a thermal vacuum valve to prevent system operation during extreme cold conditions and after the engine has reached operating temperature. Later model engines, use a solenoid, which is controlled by the ECM, to perform this function. ECM controlled systems operate only when the engine is cold or when hot and idling.
Some engines may use an addition valve assembly to prevent backfire, during the initial period of deceleration. This valve is known as the Anti-backfire (AB) valve.
Anti-Backfire (AB) Valve
See Figures 5 and 6
- Warm the engine to normal operating temperature.
- Disconnect the hose from the air cleaner and place a finger near the outlet.
- Run the engine at about 3000 rpm under no load, then return to idle. A suction should be felt. If no vacuum is felt, replace the AB valve.
MODELS WITHOUT AIV CONTROL SOLENOID
Disconnect the air induction tube from the tube leading to the exhaust manifold. Place the tube to your mouth, then suck on the tube (air should move freely through the valve); try to blow through the tube (air should not flow through it). If the valve does not respond correctly, replace it.MODELS WITH AIV CONTROL SOLENOID
See Figures 7 and 8
- Check the air valve and control valve for binding or damage. Repair or replace the valve, if required.
- Disconnect the injection hose. At the exhaust tube side, suck and blow into the hose and make sure that air flow does not exist.
- Connect a vacuum pump to the air injection control valve located at the bottom of the valve case.
- With vacuum applied to the valve, repeat Step 1. Air should flow freely to the exhaust pipe, and should not flow in the opposite direction.
- If the valve fails to perform as specified replace the AIV valve assembly.
See Figures 9 and 10
- Mark and tag all vacuum lines attached to the control valve. Once marked, remove the hoses from the control assembly.
- Apply 12V to terminal 2 , and ground to terminal 1 .
With the solenoid energized, check for air passage between vacuum fittings as follows:
Ports A and B-Passage open-air should pass freely
Disconnect the 12V power supply. With the solenoid de-energized check for air passages between the vacuum fittings as follows:
Ports A and B -Passage blocked-no air should not pass
- If the solenoid did not perform as specified, replace the EGR/EVAP solenoid/valve assembly.
- Remove the thermal vacuum valve from the engine.
- Plug one of the vacuum ports.
- Apply vacuum to the air cleaner port; it should allow vacuum to pass. Repeat the test for other port. If either port was closed, replace the vacuum valve.
Place the valve in a container of water with a thermometer. Heat the water and Repeat Steps 2 and 3. Observe the valve operation at the following temperature.
Below 59°F (15°C)-valve should be closed (vacuum should not pass)
- If the thermal vacuum valve did not perform as specified, replace the valve.