See Figures 1 through 7
The AIR management system is used to provide additional oxygen to continue the combustion process after the exhaust gases leave the combustion chamber. 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 control valve, while the check valve protects the air pump by preventing any backflow of exhaust gases.
The AIR system helps 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 warmup. 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 the CO content in the exhaust.
The system utilizes the following components:
- An engine driven AIR pump.
- AIR Control valves (Air Control, Air Switching).
- Air flow and control hoses.
- Check valves.
- A dual-bed, three-way catalytic converter.
- A deceleration back-fire control valve - 2.8L engine only.
The belt driven, vane-type air pump is located at the front of the engine and supplies clean air to the AIR 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 to 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 provides additional oxygen for the oxidizing catalyst in the second bed to decrease HC and CO, 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 problem 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 become burnable when they reach the exhaust if combined with the injection air. The next firing of the engine will ignite this mixture causing an exhaust backfire. Momentary diverting of the injection air from the exhaust prevents this.
The AIR system check valves and hoses should be checked periodically for any leaks, cracks or deterioration.
On the 2.8L engine only, an anti-backfire (gulp) valve is used to allow air flow into the intake manifold. This is used to help prevent backfire during high vacuum deceleration conditions. The extra air enters the intake system to lean the rich air/fuel mixture. The valve is operated by the intake manifold vacuum to allow air from the air filter to flow into the intake manifold.
- Remove the air cleaner and plug the air cleaner vacuum source. Connect a tachometer to the engine.
- With the engine idling, remove the vacuum signal hose from the intake manifold.
- Reconnect the signal hose and listen for air flow through the ventilation tube into the anti-backfire valve. A speed drop should be noticed when the hose is reconnected.
- If these conditions are not found, check hoses for restrictions or leaks. If hoses are OK, replace the anti-backfire valve.
- Check the drive belt tension.
- Increase the engine speed and observe an increase in air flow. If air flow does not increase, replace the air pump.
- Remove the hoses. Blow through the valve (toward the cylinder head).
- Then, suck through the valve (or blow through the other side). If air flows in one direction, the valve is operative. If not, replace the control valve.
REMOVAL & INSTALLATION
- Remove the AIR control valves and/or adapter at the pump.
- Loosen the air pump adjustment bolt and remove the drive belt.
- Unscrew the pump mounting bolts and then remove the pump pulley.
- Unscrew the pump mounting bolts and then remove the pump.
- Position the pump into place and secure it with the mounting bolts.
- Install the pump pulley.
- Install the air pump drive belt and adjust pump belt with the pump adjustment bolt.
- Install the AIR control valves and/or adapter.
- Release the clamp and disconnect the air hoses from the valve.
- Unscrew the check valve from the air injection pipe.
- Installation is in the reverse order of removal.
- 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.
- Position the valve into the elbow.
- Connect any electrical connections at the valve.
- Install the bolts holding the elbow to the valve and bend 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.