Oftentimes, mechanics like me are quick to throw around terminologies that appear confusing, one of such is the EGR (Exhaust Gas Recirculation). Over the past few decades, stricter emission standards have been set by various countries around the world to improve the quality of air that we breathe.

To meet these conditions, vehicle manufacturers have employed various strategies. These strategies include, but are not limited to the installation of components such as the EGR, evaporative emissions control system, positive crankcase ventilation system, Oxygen sensors, catalytic converters among others, our focus today will be on the EGR system.

Beginning in the 1970’s, the EGR, has been a feature of every car engine. Millions of internal combustion engines contributed enormous amounts of pollutants to the atmosphere, including nitrogen oxide (NOx). In order to help reduce levels of smog (smoke and fog) and the attendant health and environmental problems, an EGR valve is now standard equipment in every engine compartment. EGR valves are found in both gasoline and diesel powered engines and it is not difficult to locate on most engines, just follow the line from the engine to the valve, but in some engines, it is located inside a heat-resistant exhaust gas line which connects the exhaust manifold to the intake area.

The Exhaust Gas Recirculation (EGR) is a proven technique in the automotive world used in petrol and diesel engines to reduce nitrogen oxide (NOx) emissions, i.e. a technique for reducing pollutions emitted from on-road diesel engines. It works by recirculating a controlled amount of an engine’s exhaust back into the engine cylinders using a valve. This recirculation of exhaust gas, usually inert in nature, dispels and reduces the proportion of combustible matter in the cylinder. This action is known to cause a lower heat release and peak cylinder temperature, also, it reduces formation of (NOx).


  1. Potential reduction of throttling losses on spark ignition engines at part load.
  2. Improved engine life and exhaust valve lifespan through reduced cylinder temperatures.
  3. The EGR valve allows more of the fuel to be used as energy, rather than being locked up in chemical reactions.
  4. It helps to reduce the concentration of hazardous nitrogen oxides that are emitted into the environment by up to 50%.

Most vehicles are wired to trigger on a malfunction indicator lamp whenever there’s a problem in the EGR. The system is activated by a solenoid or a valve using the engine vacuum, any restriction or overflow of gas through the valve could lead to illumination of the malfunction indicator lamp, simply put, the EGR on most vehicles is purely mechanical.


As with any other part of a car, the EGR valve can deteriorate and malfunction over time. In most cases, it will be fairly easy to determine if the valve needs cleaning, repair, or replacement. The following signs will be obvious if your vehicle’s EGR is faulty or defective, which results in poor emissions and could even cause the motor to shake;

  1. Contaminants such as, soot particles, carbon deposits and oil can cause the valve to stick and potentially prevent it from opening or closing. Damage to valves may also be caused by exposure to excessively high temperatures.
  2. An engine that pings is signaling that the EGR valve is not working correctly.
  3. The engine starts to overheat as the cooler air that would be available ordinarily from the EGR is now missing.
  4. An emissions test shows that the vehicle is releasing too much nitrogen oxide into the air.
  5. Faults in other vacuum system components such as vacuum pumps, vacuum lines and solenoid valves, therefore it is always a good idea to have these checked when you do your general maintenance.
  6. In extreme cases, the engine shuts down entirely.

Clogged EGR valves can sometimes be cleaned but if an EGR valve has to be changed because of clogging, the EGR line connected to it must always be checked. If the valve is then found to be faulty, replacement is necessary.

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