An EGR valve is very important for the exhaust system in a vehicle. It has been in use since the 1960's in the US as it helps in increasing efficiency of vehicles and reducing pollution as well. However, whenever the EGR valve is clogged or not working as it should, engine performance can go down. So any time you experience rough idling or valve knock, you should have the valve inspected.
The EGR valve helps your vehicle more efficiently and completely burn fuel mixture by recirculating a portion of your exhaust and running it through the combustion process again. This results in a cooler, more complete burn of the gas which decreases you car's noxious emissions by prohibiting the formation of some harmful gases.
Symptoms of a Faulty EGR Valve
An EGR valve that is stuck open
When the EGR is stuck open, it will lead to a vacuum leak which in turn causes inefficient combustion, hesitation, rough idling and even stalling. The reason for this is that the car cannot combust on the carbon dioxide emitted from the tailpipe. An open EGR valve causes exhaust emissions to flood the combustion chamber, hence preventing it from functioning as it should. To check for a stuck open EGR valve, idle a parked car with the brake on and have someone examine the plunger shaft to see if it is stick open.
An EGR valve that is stuck closed
This causes nitrogen oxide emissions to rise and the car might start to knock. A sharp knock occurs when the fuel in the combustion chamber ignites before the explosion in the cylinder reaches it. This leads to a disruption in engine timing. When this happens, warm up your engine and rev it, then check if the EGR valve will move.