How automakers have been able to consistently build more powerful engines in vehicles that get better fuel economy while at the same meeting increasing environmental standards is quite amazing. One of the little miracles that helps make this happen is the Exhaust Gas Recirculation (EGR) Valve. What does it do? The EGR valve routes some exhaust back into the air intake system in both gasoline and diesel engines. The exhaust gas takes up some space in the engine cylinders, replacing some of the oxygen-rich air that would otherwise be in there. This means that the fuel burning event is cooler. Cooler combustion means fewer harmful nitrous oxides are produced. Pretty simple right?
What can go wrong? Well your EGR valve can get gummed up, messing the timing and amount of exhaust that is supposed to be recirculated in the engine. You’ll recognize that some of the symptoms of EGR valve problems are rough idle and poor engine performance. At that point, performance can be restored by cleaning or replacing the EGR valve, depending on how dirty it is. Note that EGR valves in diesel engines are particularly susceptible to becoming clogged because of the high soot content in diesel exhaust.
So how do you lengthen the life of the EGR valve in your diesel engine? First, extended idling allows for more soot build up because the engine operating temperature is reduced as it idles and the valve is not opening and closing, allowing particulates to accumulate in the valve. Next is fuel quality. Diesel fuel has a cetane rating: the higher the rating, the better the combustion will be. Unfortunately, the cetane rating is rarely posted on the pump and can vary from location to location. Adding a cetane booster to the fuel tank can help with this.