Air Injection Reactor System Buick Electra Estate Wagon

DESCRIPTION

Air Injection system reduces hydrocarbons (HC), carbon monoxide (CO) and nitrous oxide (NOx) emissions by injecting air into exhaust system.

A belt driven air pump injects air into either exhaust port of cylinder head, exhaust manifold or catalytic converter. Air Injection system operates at all times and will by-pass air only for a short time during rich operation, deceleration or at high speeds.

Air management valve performs by-pass and diverter function. Check valve protects air pump from damage by preventing a backflow of exhaust gases.

Air Injection System Schematic (Typical). Scheme 253

AIR PUMP

Air pump is a belt driven type vane pump, located at front of engine. Air Injection system uses filtered air from air pump to cause further oxidation (burning) of HC and CO before these gases are discharged from tailpipe.

DECELERATION VALVE

This valve is used on 2.8L engines to prevent backfiring in exhaust system during deceleration. Valve is normally closed, but opens when manifold vacuum increases during deceleration.

Vacuum overcomes spring pressure allowing additional air into intake manifold to prevent an overly rich mixture from entering combustion chambers. Air trapped in chamber above vacuum diaphragm will bleed, at a calibrated rate, through delay valve portion of integral check and delay valve.

This reducing vacuum acts on diaphragm. When vacuum load on diaphragm matches spring load, valve assembly closes. This shuts off air to intake manifold.

DIVERTER VALVE

Diverter valve is used to prevent backfire in exhaust system during sudden deceleration. Valve senses sudden increases in intake manifold vacuum causing valve to open, and divert air away from exhaust system. This allows air from air pump to pass, through valve and silencer, to atmosphere.

A pressure relief valve controls system pressure by diverting excess pump outlet air (developed at higher engine speeds) to atmosphere through silencer.

CHECK VALVE

Check valve prevents backflow of exhaust gases into Air Injection system. Check valve prevents backflow when air pump by-passes at high speeds, extreme engine loads, or in case of air pump malfunctions.

ELECTRIC AIR CONTROL VALVE

This valve combines 3 separate functions into a single valve. It provides normal diverter valve function and pressure relief by diverting air into engine air cleaner when system pressure exceeds a predetermined value.

Valve operation is controlled by a vacuum solenoid. When solenoid is energized, valve operates normally. When solenoid is de-energized, air is diverted under all operating conditions.

ELECTRIC AIR SWITCHING VALVE

Air switching valve is a spring actuated 2-way valve. This valve is located in series between air control valve and exhaust system.

When solenoid is de-energized, vacuum is applied to diaphragm chamber to provide air flow to exhaust ports.

When solenoid is energized, vacuum to diaphragm chamber is blocked and chamber is vented to atmosphere. This allows spring to open port to catalytic converter and close engine port.

ELECTRIC DIVERT/ELECTRIC AIR SWITCHING VALVE (EDES)

Electric divert/electric air switching valve (EDES) combines both air diverter valve and air switching valve into one integral component.

ECM controls air divert valve by controlling vacuum solenoid in EDES valve. EDES valve will divert air during these operating conditions: Rich conditions, deceleration, high RPM and whenever ECM recognizes a problem and sets check engine light.

ECM also controls air switching function of EDES valve by directing Air Injection flow to exhaust ports during cold engine operation (open loop), and to catalytic converter during warm engine operation (closed loop).

Sectional View of EDES Valve. Scheme 254

PRESSURE OPERATED ELECTRIC AIR CONTROL/ELECTRIC AIR SWITCHING VALVE (PEDES)

Pressure operated electric air control/electric air switching valve (PEDES) combines both diverter function and air switching function into one integral component.

PEDES valve is electrically controlled by ECM and air pump pressure operates valve. Valve's operation is not dependent on intake manifold vacuum.

For cold engine (open loop) operation, port solenoid is energized and air flows to exhaust ports. In warm engine (closed loop) operation, port solenoid is de-energized and converter solenoid is energized which forces air flow to converter. In divert mode, both solenoids are de-energized and air flow is allowed to vent to atmosphere.

Sectional View of PEDES Valve. Scheme 255

COMPONENT TESTING

Note. For Air Management System Function Check, Electric Air Control/Electric Air Switching Valve check and Electric Diverter Valve check, see Diagnostic Charts in the COMPUTER COMMAND CONTROL article.

1. Detach check valve and blow though it in direction of flow to cylinder head. Attempt to suck back through direction of flow. Replace valve if it allows airflow against direction of flow.
2. If air pump was inoperative and had signs of exhaust gases reaching pump, a failed check valve would be indicated.

1. Accelerate engine to approximately 1500 RPM and observe air flow from hoses. If airflow increases as engine is accelerated, pump is operating properly. If it does not increase, or is not present, proceed to next step.
2. Check for proper pump belt tension, leaky valves, seized pump, improperly routed hoses or disconnected hoses.

Note. DO NOT oil air pump. The air pump system is not completely noiseless.

1. Remove air cleaner, plug air cleaner vacuum source and connect tachometer to engine. With engine running at idle, remove deceleration valve signal hose from intake manifold.
2. Reconnect signal hose and listen for air flow through ventilation pipe and into deceleration valve. Engine speed should drop when hose is reconnected.
3. If air flow lasts less than 1 second or engine speed does not drop, check for defective hoses or deceleration valve.

EXHAUST BACKFIRE

1. Engine not tuned to specifications.
2. Engine vacuum leaks.
3. Faulty diverter valve or check valve.
4. Electric air switching valve or air control valve not switching air pump discharge to air cleaner on start or quick deceleration.

POOR GAS MILEAGE

1. Air pump output not shifting to catalytic converter upon signal from TVS.
2. Faulty electrical and/or vacuum circuits.