Engine Management
EGR TechnologySymptoms and Causes of EGR Failure The recirculated exhaust gas contains both gaseous pollutants and soot particles, in particular on diesel-engine vehicles. If oil is added to the intake air, cases of carbon-fouling or sticking can occur which, at some point, the force of the valve can no longer cope with – the EGR valve cannot be opened or remains in its open state. The consequences are: 1. Jerking 2. Irregular idling 3. Lack of power There may be various causes for an intensely oily intake or charge air. These causes may include:
Routine causes as outlined below can also result in sticking EGR valves:
Unusually thick deposits can also be caused by faults in the injection system. Although EGR valves are designed for the high temperatures that occur in the exhaust branch, the valve may occasionally suffer from thermal damage. The causes may be incorrect actuation, excessive exhaust gas back pressure or a non-opening blow-off valve ("wastegate valve") of the turbocharger. It may even be a matter of deliberate manipulation to increase the boost pressure. Adaptation A relatively new form of claims on EGR valves are complaints such as "new part without function". If a new EGR valve is installed after a failure and the vehicle behaves as if the valve had not been replaced, the engine control unit must first "get to know" the new valve through a process known as "adaptation". Adaptation can be completed by undertaking a longer test drive or by using a specific program option of the diagnostic tool.
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