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Car petrol engine design has taken a massive leap over the last 10 Years, with advances such as 16 valve twin cam injection engines now being standard, but now appears to have reached a plateau. Tightening exhaust emission regulations though are continuing to make more strange looking emission control devices to appear on modern engines – one of these is the EGR valve or Exhaust Gas Re-circulation valve. This device takes
some of the exhaust gas that would otherwise go out of the exhaust tail pipe and feeds it back into the inlet air/petrol system. The reason for doing this is to lower the temperature of the combustion process, this reduces the level of oxides of nitrogen ( or NOX) emissions. The amount of exhaust gas that is re-circulated must be well controlled – or like re-cycling all of your own breath back in again it will cause running problems. Recently we have had a spate of problems with EGR valves causing hesitations, stalling at idle, and rough idling. With all of our EGR faults though nothing was registered on the car’s diagnostic system because it was sending out the right signals to the valve. The diagnostic system though had no way of knowing if the EGR valve was responding to the signals as it should. – ours were sticky in operation. Fortunately we were able to un-stick them with specialist cleaning equipment. (Price for a new EGR valve could make your eyes water – well in excess of £100 for some cars.) . Gone are the days when all that was needed to get you out of misfiring trouble was a set of plugs and leads
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