In most internal combustion engines the EGR or exhaust gas recirculation is used to reduce emissions in petrol and diesel powered engines. The EGR recirculates part of the engine’s exhaust gasses back into the engine’s cylinders where it is burnt. The EGR valve is responsible for controlling the flow of these usually NO2 gasses into the intake manifold. The constant opening and closing of the valves can lead to it becoming faulty. Usually, the value along with the intake manifold needs to be examined and replaced when there is a problem with the EGR system as a whole.
When the EGR valve fails, it can either fail as open or close. Usually, you’ll experience rough idle when the car is started up. Constant stalling when the engine is idle, unusually high fuel consumption, fuel odor, emissions test failure, the engine check light will glow, etc. In some cars, you’ll also hear tapping noises which is another indicator of a problem in the intake manifold. If you experience these symptoms its best to visit a professional mechanic who will examine the vehicle and determine if the EGR system needs to be fixed.
When in the market for an EGR valve it is important to note that there are various types out there. So, it's best to only buy ones that match the part number of the existing value. Fortunately, you can search and purchase a valve at car-parts.ie via part number, while saving time and money.