Q: My truck set a code several months ago for the EGR valve. At that time I really wasn’t noticing any problems. Since then, the truck has started jerking or bucking around 45 or 50 MPH. If you accelerate the problem seems to go away. It also has a roaring sound, when you let off the gas and coast down to make a stop. You can here the roaring sound when the car is idling but as soon as you press the accelerator the sound goes away or gets really faint. What is the purpose of the EGR valve?
A: The purpose of the EGR (Exhaust Gas Recirculation) valve is to lower the oxides of nitrogen (N0x). It controls the quantity of exhaust being directed back into the intake manifold, actually to cool the combustion process. An EGR valve that is not functioning properly can cause jerking, hesitation, or rough idling.