A diesel engine creates heat only when it is under loads. When it is idling, it is running very cold. If a diesel engine is not being pushed then it is not going to burn off these hydrocarbons especially with idle times like this where a truck will sit for 10, 12, 14 hours just idling. So you get this buildup inside. This is a common EGR clog EGR systems are widely applied in modern turbocharged diesel engines to reduce engine-out emissions and will, or are being used to mitigate engine knock in SI engines for improved SI engine The EGR valve operates in a harsh environment and it therefore prone to failure. We therefore offer our customers the option of removing the EGR system from the engine management programme. In this instance the EGR valve would be driven closed and the pipework physically blanked off to ensure that exhaust gasses cannot enter the engine. On engines such as the 6.4L Power Stroke and 6.7L Power Stroke, there are two EGR coolers at work. Diesel Particulate Filter (DPF) When the federal government tightened the noose around PM emissions in 2007, not even the maximized efforts of high-pressure common-rail injection were efficient enough to meet the new standard. The EGR system returns the engine exhaust gases back to the engine cylinder. During this process, it reduces the temperature of the exhaust gases and the oxygen level in the cylinder of the engine. Both factors inhibit the formation of NOx. In this way, the EGR valve controls the emission of exhaust gases. The EGR valve is a small component that is designed to facilitate the movement of gases in and out of the combustion chamber by simply opening and closing the valve. The role of the EGR stays the same irrespective of the engine system configuration. Like everything in nature, these EGR valves also have limitations and tend to fail. Exhaust Gas Recirculation (EGR) complete guide – architectures. Exhaust gas recirculation (EGR) is the most common technology to reduce nitrogen oxides (NOx) emissions on diesel internal combustion engines (ICE). EGR takes exhaust gases from the exhaust manifold and reintroduces them into the intake manifold, mixing them with fresh air. My understand of the egr system. It reciruates a percent of exhaust gases back into the intake system. Emissions 101. This is to reduce the pollutants that go out the pipe. On the the 6.4 and others the percentage of egr is determined by the amount needed because of the epa. Hence more egr, worse mileage. iRKe6c.