Emission Control Systems – Must perform, many important jobs.

Consequently, emission control systems, have been efficient; in reducing air pollution, caused by automotive engines.

So, emission control systems, depend on a series of chemical reactions; sensors and vacuum controlled solenoids, to operate correctly.

That’s why, emission control systems, rely on many other supporting systems, to function properly.

But, in time, chemical reactions fade, as the devices lose their effectiveness. Consequently, any of these failures, will cause a check engine light to come on.

In addition, excessive idling wastes money and fuel; while producing greenhouse gases, that contribute to climate change.

Engine Generated Pollutants, Come From Three Sources:

1. Tailpipe exhaust.
2. Crankcase blow by fumes.
3. Fuel fumes, that evaporate from the fuel tank.

Air Pollution Gases, Produced By Engines, Consist Of:

• Carbon monoxide.
• Hydrocarbons.
• Carbon dioxide.
• Nitrogen oxide.

Most Emission Control Systems, Consist Of:

• Air Pump.
• Catalytic Converter.
• Check Engine Light (CIL).
• Exhaust Gas Recirculation (EGR).
• Automotive Filters.
• Gas Cap.
• Evaporative System.
• Mass Air Flow Sensor (MAF).
• OBD-II System.
• Oxygen Sensor (O2).

Air Pump

Air injection systems, have become more diverse in nature. Sometimes, using the on board computer, to control system operations. Similarly, some engines use, pulse air systems, that do not use a pump.

As obsolete as this technology seems, some late model vehicles; use a high tech air injection system. Usually, using an electric air pump, controlled by the vehicles; Powertrain Control Module (PCM). Furthermore, improving, emission control systems.

Catalytic Converter

The catalytic converter, looks like a muffler. It is located in the exhaust system, ahead of the muffler. Inside the converter are pellets or a honeycomb, made of platinum or palladium. The platinum or palladium, is used as a catalyst.

Consequently, as exhaust gases are passed over the catalyst; they are chemically oxidized or converted to carbon dioxide and water. So, as the converter works to clean the exhaust, it also develops heat. The dirtier the exhaust, the harder the converter works. As a result, the more heat that is developed. Consequently, if the converter works too hard to clean a dirty exhaust, it will destroy itself.

(EGR) Valve

So, the (EGR) valve, has no recommended replacement or inspection interval. But, that doesn’t mean it won’t cause trouble.

So, (EGR) reduces the formation of oxides of nitrogen. Consequently, by diluting the air/fuel mixture with exhaust. As an added benefit, (EGR) also helps prevent detonation.

Filter Systems

Above all, the oil filter, traps harmful debris, from being; recirculated back through the engines lubrication system. Also, the air filter, stops harmful dirt particles, from; entering the engines air intake system; where they may cause engine damage.

The crankcase breather filter, cleans the air pulled into the engine crankcase. Consequently, by using the positive crankcase ventilation (PCV) system. The fuel filter cleans the fuel, before it reaches the fuel delivery system; namely the fuel injectors. Furthermore, the canister filter, cleans the air entering the carbon canister; that is part of the emission control system.

Gas Cap

Consequently, a gas cap, seals liquid fuel and fumes; from leaking or escaping from the fuel tank.

The gas cap, is also an integral part; of the onboard diagnostics system (OBD-II) and emission control systems.

Evaporative System

The evaporative system, sometimes abbreviated as (EVAP), consists of the:

• Fuel cap.
• Fuel tank.
• Carbon canister.
• Canister purge valve.
• Interconnecting lines and hoses.

However, sealing the fuel tank, is not as simple as it sounds. A fuel tank must have some type of venting; so air can enter, to replace the fuel leaving the tank.

If the fuel tank were sealed tight; the fuel pump, could create enough negative pressure, to collapse it. This system contains fuel fumes (hydrocarbons). But, instead of releasing them into the atmosphere, it stores them in a carbon canister. The collected fumes, are then routed to the engine, where they can be burned.

Mass Air Flow (MAF) Sensor

Finally, a mass air flow sensor, monitors airflow that enters the engine.

OBD-II System

The SERVICE ENGINE SOON or CHECK ENGINE LIGHT has several modes. It can also do a , self check on the system.

P0400-P0499 – Auxiliary Emissions Controls. OBD-II

Consequently, It can indicate a:

• Normally functioning system.
• A system that requires, prompt attention.
• A system that needs, immediate attention.