Air Injection System Cadillac Brougham I

DESCRIPTION

The air injection system is designed to reduce hydrocarbons (HC) and carbon monoxide (CO) emissions by injecting air into the exhaust manifold(s) or catalytic converter.

A belt driven air pump injects air into the exhaust port of cylinder head, exhaust manifold or catalytic converter. The air injection system operates at all times and will by-pass air during rich operation, deceleration, cold engine operation or high RPMs.

There are 4 different air injection system valves used to direct proper air flow. A check valve protects the air pump from damage by preventing a backflow of exhaust gases.

Scheme 29

AIR PUMP

The air pump is a belt driven, positive displacement vane-type pump. The air pump is permanently lubricated and requires no periodic service. The air injection system injects filtered air into the exhaust manifold and/or catalytic converter.

Note. Always cover centrifugal filter fan before cleaning engine to prevent liquid from entering air pump. DO NOT oil air pump.

DIVERTER/DECELERATION VALVE

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

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

CHECK VALVE

The check valve prevents the backflow of exhaust gases into the air injection system. The check valve operates when the air pump by-passes at high speeds, extreme engine loads or when air pump malfunctions.

AIR MANAGEMENT SYSTEM

Note. These valves may be separate or combined.

Electric Air Control Valve

This valve provides normal diverter valve function and pressure relief by diverting air into the engine air cleaner when system pressure exceeds a predetermined value. Valve operation is controlled by a vacuum solenoid. When the solenoid is energized, valve operates normally. When the solenoid is de-energized, air is diverted by operating conditions.

Electric Air Switching Valve

The air switching valve is a spring actuated 2-way valve. This valve is located in series between air control valve and exhaust system. When the solenoid is de-energized, vacuum is applied to diaphragm chamber, resulting in airflow to exhaust ports. When the solenoid is energized, vacuum to diaphragm chamber is blocked and chamber is vented to atmosphere. This allows spring tension to open port to the catalytic converter and close engine port.

ELECTRIC DIVERT/ELECTRIC AIR SWITCHING VALVE (EDES)

Electric Divert/Electric Air Switching Valve (EDES) is used on 5.0L (VIN Y) and combines the functions of both the air diverter valve and air switching valve into one integral component. (Scheme 30)

The ECM controls the air divert valve by controlling the vacuum solenoid in the EDES valve. The EDES valve will divert air during these operating conditions: rich conditions, deceleration and high RPM. The EDES valve will also divert air whenever ECM recognizes a problem and turn on "SERVICE ENGINE SOON" (SES) light.

The ECM also controls the 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).

Scheme 30

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

Pressure Operated Electric Air Control/Electric Air Switching Valve (PEDES) is used on all Federal vehicles except (5.0L VIN Y and W Body 2.8L and 3.1L manual transaxle) combines both diverter function and air switching function into one integral component. (Scheme 31)

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

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

Scheme 31

ELECTRIC DIVERTER VALVE

The Electric Diverter Valve (EDV) is used on California fuel injected models and 2.8L and 3.1L W Body manual transaxle models. This EDV performs normal diverter valve operation and may provide air divert to the air cleaner for catalytic converter protection during wide open throttle and high temperature conditions.

The ECM de-energizes EDV solenoid (located in EDV), preventing manifold vacuum from entering the chamber during the above conditions. Spring tension against the lower diaphragm pushes the diaphragm up, diverting air to air cleaner. Air from the air pump is always shut off from the engine unless ECM grounds EDV circuit (solenoid energized). (Scheme 32)

Scheme 32

COMPONENT TESTING

Note. For air management system diagnosis, see appropriate chart in the COMPUTERIZED ENGINE CONTROLS section.

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

1. Accelerate engine to approximately 1500 RPM and observe airflow from hoses. If airflow increases as engine is accelerated, pump is operating properly. If airflow 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. It is normal for air pump to emit some noise, especially during deceleration, when air is exhausted into atmosphere.

DECELERATION VALVE

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 while listening for airflow through ventilation pipe and into deceleration valve. Engine speed should drop when hose is reconnected.
3. If airflow lasts less than one second or engine speed does not drop, check for defective hoses or deceleration valve.

EXHAUST BACKFIRE

1. Check for engine vacuum leaks and/or engine not tuned to specifications.
2. Check for faulty diverter valve or check valve.
3. Check for electric air switching valve or air control valve not switching air pump discharge to air cleaner during engine starting or deceleration.

POOR GAS MILEAGE

Check air pump output not shifting to catalytic converter upon signal from TVS and/or faulty electrical and/or vacuum circuits.

EXCESSIVE EXHAUST EMISSIONS

Check that air is not being diverted to exhaust manifold during normal engine operation and that air is being diverted to catalytic converter during normal engine operation.