The EGR Valve and System – It’s Just Three Letters, but EGR Can Lead to AGGravation.
Common in automotive emission systems since the early 1970s, the EGR (Exhaust Gas Recirculation) valve controls a vehicle’s emissions of nitrous oxides or NOx. Its job is to route some exhaust gas back to the intake manifold. This lowers the combustion temperature to below 2500 degrees Fahrenheit – the temperature at which NOx gases form.
EGR flow is controlled by the engine computer, which opens or closes the valve as needed. The EGR system is, for the most part, in the “out of sight, out of mind” category and generally doesn’t require regular maintenance. But if it becomes clogged with carbon deposits, you’ll see your “check engine” light come on, and a code (perhaps P0401 or P0402 or P0403) will indicate insufficient flow. This usually results from consistently driving a vehicle on short trips that don’t allow the engine to fully warm up. Flow problems can also be caused by carbon buildup due to failing to change the oil frequently enough.
A clogged EGR valve not only leads to increased emissions, but it can also reduce fuel economy and cause rough idling, or even serious engine damage. Valves can usually be cleaned, but replacement is often recommended.
Tip?
Make sure to drive highway or freeway miles and always change the oil according to the maintenance schedule in the owner’s manual.