With the exception of the 231 V6 engine (which does not use a dual-bed converter and is equipped with the standard AIR system through 1984) the air management system was used on most vehicles 1981 and later. The air management system is used to provide additional oxygen to continue the combustion process after the exhaust gases leave the combustion chamber; much the same as the AIR system described earlier in this section. Air is injected into either the exhaust port(s), the exhaust manifold(s) or the catalytic converter by an engine driven air pump. The system is in operation at all times and will bypass air only momentarily during deceleration and at high speeds. The bypass function is performed by the air management valve, while the check valve protects the air pump by preventing any backflow of exhaust gases.
The AIR system helps to reduce HC and CO content in the exhaust gases by injecting air into the exhaust ports during cold engine operation. This air injection also helps the catalytic converter to reach the proper temperature quicker during warm-up. When the engine is warm (closed loop), the AIR system injects air into certain beds of three-way converter in order to lower the HC and CO content in the exhaust.
The Air Management System utilizes the following components:
- An engine driven air pump
- Air management valves (Air Control and Air Switching)
- Airflow and control hoses
- Check valves
- A dual-bed, three-way catalytic converter.
The belt driven, vane-type air pump is located at the front of the engine and supplies clean air to the system for purposes already stated. When the engine is cold, the Electronic Control Module (ECM) energizes an air control solenoid. This allows air to flow to the air switching valve. The air switching valve is then energized to direct air into the exhaust port.
When the engine is warm, the ECM de-energizes the air switching valve, directing the air to the catalytic converter. This provides additional oxygen for the oxidizing catalyst in the second bed in order to decrease HC and CO levels. At the same time this keeps oxygen levels low in the first bed, which enables the reducing catalyst to effectively decrease the levels of NO x .
If the air control valve detects a rapid increase in manifold vacuum (deceleration), certain operating modes (wide open throttle, etc.) or if the ECM self-diagnostic system detects any problems in the system, air is diverted to the air cleaner or directly into the atmosphere.
The primary purpose of the ECM's divert mode is to prevent backfiring. Throttle closure at the beginning of deceleration will temporarily create air/fuel mixtures which are too rich to burn completely. These mixtures will become burnable when they reach the exhaust if they are combined with injection air. If this was allowed to occur, the next firing of the engine would ignite the mixture causing an exhaust backfire. Momentary diverting of the injection air from the exhaust prevents backfiring.
The air managements system's effectiveness depends upon a properly maintained and tuned engine control system. Refer to the engine tune-up procedures in of this guide for more information on engine settings. In addition to engine control adjustments, all hoses and fittings should be inspected for condition and connection tightness. The drive belt and air filter should be checked periodically and replaced, as necessary.
REMOVAL & INSTALLATION
- Disconnect the valves and/or adapter at the air pump.
- Loosen the air pump adjustment bolt(s) and remove the drive belt.
- Unscrew the mounting bolts and then remove the pump pulley.
- Unscrew the pump mounting bolts and then remove the pump.
- Position the pump in the vehicle, then install the mounting bolts.
- Install the pump pulley and tighten the mounting bolts.
- Position the drive belt over the pulley, then adjust the belt tension and tighten the adjusting bolt(s).
- Connect the valves and/or adapter to the air pump.
- Release the retaining clamp, then disconnect the air hoses from the valve.
- Unscrew and remove the check valve from the air injection pipe.
- Install the check valve to the air injection pipe, then carefully tighten.
- Make sure the hoses are properly positioned, then connect them to the valve.
- Position and secure the retaining clamp to the hoses.
- Disconnect the negative battery cable.
- Remove the air cleaner assembly.
- Tag and disconnect the vacuum hose(s) from the valve.
- Tag and disconnect the air outlet hoses from the valve.
- Bend back the lock tabs and then remove the bolts holding the elbow to the valve.
- Tag and disengage any electrical connections at the valve, then remove the valve from the elbow.
- Position the valve in the vehicle and install it to the elbow, then engage the electrical connections, as noted during removal.
- Tighten the retaining bolts, then bend the lock tabs into position.
- Connect the air outlet hoses to the valve, as noted during removal.
- Connect the vacuum hose(s) to the valve, as noted during removal.
- Install the air cleaner assembly.
- Connect the negative battery cable.
- Remove the drive belt and pump pulley.
- Using needle nose pliers, carefully pull the fan from the pump.
Use care to prevent any dirt or fragments from entering the air intake hole. DO NOT insert a screwdriver between the pump and the filter, and do not attempt to remove the metal hub. It is seldom possible to remove the filter without destroying it.
- To install a new filter, draw it on with the pulley and pulley bolts. DO NOT hammer or press the filter on the pump.
- Draw the filter down evenly by torquing the bolts alternately and evenly. Make sure the outer edge of the filter slips into the housing. A slight amount of interference with the housing bore is normal.
The new filter may squeal initially until the sealing lip on the pump outer diameter has worn in.