Egr Valve
TheEGR valveis part of the exhaust gas recirculation (EGR) system on your car. The system allows exhaust gases to enter the combustion chamber to cut nitrogen oxide (NOx) emissions. However, an EGR valve may stay closed and cause the engine to detonate after warming up, or remain opened and cause the engine to idle rough or stall when cold. Also, gas passages may become clogged, or the valve itself may become damaged. However, a few simple tests can help you find the source of the problem and restore engine performance. Keep in mind, though, that these tests only apply to vacuum operated EGR valves.Is the stem inside the EGR valve stuck?First, you want to make sure the diaphragm inside the valve is able to move up and down. If you have good access to the valve, you might be able to stick your finger through one of the valve openings and try to move the stem up and down. If your finger doesn't fit through the opening, you can start the engine and let it idle as you open the throttle manually to about 2,500 rpm. Watch for diaphragm movement using a small mirror, if necessary.Another way to do this is to unplug the vacuum line from the top of the valve and plug ahand vacuum pumpin its place. With the engine off, apply a small amount of vacuum. Use a small mirror to check if the stem moves.If the stems is free to move, but you know the diaphragm doesn't move with an increase in engine speed, check for vacuum with the engine at idle. Unplug the vacuum hose from the EGR valve and place your finger at the hose opening. You should feel the pull from the vacuum as you increase engine rpm. Otherwise, check for an obstruction or a vacuum leak between the hose and the intake manifold.Some Ford models use pressure instead of vacuum to operate the EGR valve. In this case, you should feel a slight push on your finger as you increase engine speed.If there is vacuum or pressure, but you know the stem or diaphragm doesn't move with an increase in engine speed, you can remove the valve and clean carbon deposits from underneath the valve and intake passages that might be affecting valve operation. If this doesn't fix the problem, replace the valve.Is the valve stuck in the closed position?One reason your EGR valve might get stuck in the closed position is a punctured diaphragm. Even a small pinhole can prevent vacuum or pressure from opening the valve. An easy way to test the diaphragm is using a can of carburetor cleaner. Start the engine, let it idle, and apply the parking brake. If necessary, block the wheels with wooden blocks.Attach the small red straw that comes with the product to the can of carburetor cleaner. Spray cleaner around the diaphragm through the valve openings and listen carefully for any changes in engine speed. If engine speed changes momentarily as you apply the cleaner, the diaphragm is punctured. Replace the EGR valve.Testing valve operationSometimes, you need to check the EGR valve as it operates to see if gases are actually flowing through or not. For this test, you'll use a hand vacuum pump. Start the engine and let it idle for 10 to 15 minutes to allow the engine to reach operating temperature.With the engine running, unplug the vacuum hose from the EGR valve and block the hose opening with a suitable Phillips-head screwdriver, a nail or golf tee. Connect the hand vacuum pump in place of the vacuum hose and gradually apply 15 in-Hg of vacuum to the valve. At the same time, you can watch if the valve stem is moving using a small mirror. At this point, several things may happen.If exhaust gases are flowing through, you should notice the engine beginning to idle rough or stall. If you know the valve stem is moving, but there's no change in engine performance, you know gas passages are restricted. You may try removing the valve and cleaning carbon deposits from the passages or replace the EGR valve, if necessary. Also, you may notice that the valve doesn't move at all or is not able to hold vacuum. In this case, you will need to replace the valve.Blocked exhaust gas passages is one of the most common problems you'll see happening with your EGR valve due to carbon deposits. In fact, many car manufacturers recommend checking the valve at regular intervals to make sure the valve is working properly and exhaust gases are flowing unrestricted. However, EGR valves may fail to operate after miles of service as well. Using these simple tests will help you figure out the cause of the problem before you decide to replace it and help youemission systemwork properly.
