The most common signs of a bad exhaust gas recirculation valve are rough or idle misfiring, detonation, stalling and a hard starting. The EGR valve is a unit of an automobile’s exhaust circulation system that assists in reducing pollution-causing emissions
When an EGR valve behaves incorrectly by leaking, getting clogged or malfunctions, it leads to poor engine performance. Because of the mechanical nature of the EGR valves, they are given to becoming stuck in opened and closed positions. EGR valves that are stuck open produce poor idling, engine misfiring and often times stalling. If the valve is closed, a nitrogen oxide builds up causing knocking and incorrect engine timing.
Mechanics can check for other causes by using the vacuum gauge to check for sufficient vacuum supply. If there is no vacuum, it shows a leak in the system. Mechanics can also inspect the EGR valve stem to see if it moves while the engine is revving. If it does not move, the valve is bad and needs a replacement. The valve also needs to be examined for clogs and cleaned or replaced, where necessary.
In view of the facts that the EGR valve problems have a range of causes, the best way to diagnose the problem is to use a scanning tool that shows trouble codes. Most vehicle repair manuals list the proper repair protocol depending on the trouble codes.