See Figures 1 and 2
The Air Management system is used on 1981 and later vehicles to provide additional oxygen to continue the combustion process after the exhaust gases leave the combustion chamber; it works in much the same way 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 contents 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 the beds of a three-way converter 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)
- Air flow 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 blow to the air switching valve. The air switching valve is then energized to direct air into the exhaust ports.
When the engine is warm, the ECM de-energizes the air switching valve, thus directing the air between the beds of the catalytic converter. This then provides additional oxygen for the oxidizing catalyst in the second bed to decrease HC and CO levels, while at the same time keeping oxygen levels low in the first bed, enabling the reducing catalyst to effectively decrease the levels of NOx.
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. The next firing of the engine will ignite the mixture causing an exhaust backfire. Momentary diverting of the injection air from the exhaust prevents this.
The air management system check valves and hoses should be checked periodically for any leaks, cracks or deterioration.
This effectiveness depends on correct engine idle speed and ignition timing. These settings should be strictly adhered to and checked frequently. All hoses and fittings should be inspected for condition and tightness of connections. Check the drive belt for wear and tension every 12 months or 12,000 miles.
REMOVAL & INSTALLATION
- Disconnect the negative (-) battery cable. Remove the valves and/or adapter at the air pump.
- Loosen the air pump adjustment bolt and remove the drive belt.
- Unscrew the three mounting bolts and then remove the pump pulley.
- Unscrew the pump mounting bolts and then remove the pump.
- Be sure to adjust the drive belt tension after installing the pump.
- Install the three mounting bolts and adjust the belt to 146 ft. lbs. for a new belt and 90 ft. lbs. for an old belt.
- Torque the air pump adjustment bolt to 25 ft. lbs. (34 Nm).
- Connect the negative (-) battery cable. Install the valves and/or adapter at the air pump.
- Disconnect the negative (-) battery cable. Release the clamp and disconnect the air hoses from the valve.
The valve may be seized to the injection pipe due to rust. Soak the fitting with penetrating oil for an hour or two before attempting removal. Always use a backup wrench when attempting to remove the valve.
- Unscrew the check valve from the air injection pipe.
- Install the valve and torque to 30 ft. lbs. (41 Nm). Connect all disconnected hoses and negative battery cable.
- Disconnect the negative battery cable.
- Remove the air cleaner.
- Tag and disconnect the vacuum hose 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 disconnect any electrical connections at the valve and then remove the valve from the elbow.
- Install the valve and connect any electrical connections at the valve.
- Torque the valve bolts to 10 ft. lbs. (14 Nm) and bend back the lock tabs.
- Connect the air outlet hoses to the valve
- Connect the vacuum hose to the valve.
- Install the air cleaner.
- Connect the negative battery cable.
- Remove the drive belt and pump pulley.
- Using needlenose pliers, pull the fan/filter unit from the pump hub.
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 onto the pump.
- Draw the filter down evenly by torquing the bolts alternately. 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.