What Will Blocking the EGR Do?

by Jay Motes
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A vehicle's Exhaust Gas Recirculation (EGR) system reduces the amount of emissions released into the atmosphere. Blocking the EGR will result in an increase in emissions as well as problems with the engine and exhaust system.


The EGR system is designed to reduce emissions, specifically the creation of NOx. NOx is the combination of nitrogen and oxygen at high temperatures during combustion. A blocked EGR will result in an increase of NOx as well as hydrocarbon emissions that pollute the atmosphere and may cause an automobile to fail an emissions test.

Exhaust Damage

The EGR system reduces emissions by preventing the combustion temperature in the engine from reaching 2800 degrees Fahrenheit, the point at which NOx is produced. When the EGR system malfunctions, the engine temperature will increase. This will not only increase emissions, but the hotter exhaust gases may also cause increased wear and possible failure of the exhaust system.

Gas Mileage

A blocked EGR system can result in detonation, often referred to as spark knock. Detonation is caused when fuel is injected into the cylinder and is ignited by the heat in the cylinder and not the spark from the ignition system. This early burning of the fuel makes the engine run inefficiently, increasing fuel consumption and wear on the engine.

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