The EGR valve system in your car is designed to reduce emissions. Under certain driving conditions, such as high load or idle, the engine will automatically turn on the EGR valve to allow exhaust gas to re-enter the combustion chamber and be burned with new fuel. The EGR valve is designed to close when not needed so that no excessive pressure builds up in the system.

What is EGR?

EGR stands for Exhaust Gas Recirculation. It’s a process that allows unburned fuel in the exhaust to be drawn back into the engine to be burned with fresh fuel. This reduces the number of emissions that are released from the engine.
When the EGR valve system fails, you will notice abnormal smoke coming from the tailpipe and poor fuel economy. The reason for this is that unburned exhaust gas has been entering the combustion chamber creating high levels of carbon monoxide (CO) which then gets passed onto the catalytic converter where it doesn’t get converted into less harmful emissions. When this happens your car will lose power and the engine will run rough. 

Parts of an EGR Valve

There are two main components in the EGR valve system: the EGR valve itself, which is found underneath the intake manifold, and the EGR cooler, which is located behind the exhaust manifold. The function of these two components is to reduce emissions by allowing unburned fuel in the exhaust to be drawn back into the engine. 
The EGR valve itself is a stepper motor-controlled solenoid. When power from the PCM is applied to the EGR valve, it will open up. When not needed, the valve will close by itself due to a spring that is built into the component. The EGR cooler’s job is to cool down the exhaust gas after it has been drawn back into the engine so that fewer emissions are released from the tailpipe.

Diagnosing EGR Valve Failure

There are two ways to diagnose an EGR valve system failure. The first way is by performing an emissions test and the second way is by doing an OBD II scan. If your car fails either of these tests, it will indicate that there is something wrong with your EGR valve system.
The emission test involves driving your car on a dynamometer while being monitored by a technician. This allows the technician to monitor how much pollution your car is emitting. If the amount of pollution is above the acceptable limit, then it indicates that there is a problem with your EGR valve system and/or catalytic converter.
The OBD II scan will indicate if any trouble codes have been set due to problems within the engine management system or emissions control systems. If no trouble codes are found, but there is an indication of a failed test, this will also indicate a problem with the EGR valve system and/or catalytic converter.
EGR valve system failure can be caused by a number of different problems. The first one is a bad EGR valve itself. This can happen due to excessive wear and tear or corrosion from engine oil and fuel that has leaked onto it. Another problem that can cause failure for the EGR valve system is clogged passages in the intake manifold, which will block the flow of exhaust gases into the engine.

Common Causes for EGR Valve Failure

The two main causes of failure for the EGR valve system are excessive wear and corrosion. Most of the time, when these components fail they will require replacement. The most common causes of EGR valve system failure are:
The EGR cooler’s job is to cool down the exhaust gas that has been drawn back into the engine so that it will not release too much pollution when released from the tailpipe. When this happens, the cooler is unable to do its job and this will cause an increase in emissions. The most common causes for EGR cooler failure are:

Replacing an EGR Valve

The first step to replacing your EGR valve system is to disconnect the negative battery cable from the battery. You will want to make sure that you disconnect the negative cable from the battery, not the positive side. When choosing an EGR valve buy one that’s compatible with your vehicle.

Next, you should remove the intake manifold and EGR valve. Once this has been done, you can go ahead and replace the old components with new ones. Once you have replaced all of the necessary parts it will be time to put everything back together again. Make sure that you do not forget any steps in order to avoid damage to your engine or other components of your car.
Now that you have replaced the EGR valve system, it is time to do a test drive. Go for at least fifteen minutes on an open road with no stop signs or red lights in order to get the car running properly again. If your car still has problems after this test drive, then there may be something else wrong with it. You should go back and check all of the steps again to make sure they were done correctly.