Exhaust emissions, when not properly controlled, are not only harmful to the environment but to the engine as well. How is this possible? When the combustion temperature reaches above 2,500 degrees Fahrenheit, nitrous oxides are formed. This means that nitrogen mixes with the oxygen in the air at such temperature. These nitrous oxides, when combined with hydrocarbons during hot weather, can form smog.
The Exhaust Gas Recirculation Valve or EGR Valve helps in efficiently facilitating the flow of an accurate amount of exhaust into the engine by opening a small passageway between the exhaust and the intake manifold. By performing this task, the EGR Valve plays a part in keeping the engine temperature at a low level and in minimizing the engine's exhaust emissions. Moreover, the EGR valve can also contribute to reduced throttling losses and chemical dissociation.
The first EGR Valves were used in the 1970s. These were simple, using only manifold vacuum. As a result, vehicles with EGR valves back then experienced deterioration in performance and drivability. In the 1980s, however, the EGR valves were equipped with a coolant temperature sensor which only enabled the EGR system after the engine reached the normal operating temperature. Today, the EGR valve is already available in two types. The first one is powered by a vacuum, while the other one is operated by pressure. These types lower the engine's temperature by letting the exhaust emissions in when the engine temperature starts to increase. However, modern vehicles manufactured nowadays make use of electronic EGR valves.
To achieve the EGR valve's maximum performance, one must keep it closed while the engine is cold and idle. It should only be opened when the engine has already warmed up and is already running. One must also ensure that the valve sticks are not disconnected because failure to do so will cause an increase in nitrous oxides and detonation. Moreover, one must check if the valve sticks are closing properly since they can cause a vacuum leak that may lead to hesitation, rough idle, and stalling of the engine.