Troubleshooting the EGR System

A vehicle’s exhaust gas re-circulation (EGR) system is designed to return a specific amount of exhaust back into the engine’s intake. The result is a reduction of nitrogen oxide released into the atmosphere. When an EGR system is malfunctioning, a vehicle’s engine will have a rough idle if the EGR valve sticks in an open position. If the valve is closed, an engine will have a pinging and knocking sound. Troubleshooting this system requires a little time and tools such as a ratchet set to begin. Follow these instructions to test the system for failure.



Find the EGR Valve

The vehicle’s service or owner’s manual will provide information on where the valve is located. Once it is found in the manual, open the hood for observation.


Inspect All Hoses

After finding the EGR valve, it is necessary to check each hose that is attached to the valve and EGR system for brittleness or broken sections.


Check for Pressure at the Stem

If possible, use your finger or an object that is small enough to press the valve stem against the pressure spring. If the stem moves freely, the valve stem is operational. If it does not move, cleaning it or replacing it is the best option.


Check Proper Operation of Valve Stem

With the help of a friend, turn on the vehicle’s engine. Have the friend apply pressure to the accelerator until the RPM registers above 2000. Pay close attention to movement in the valve stem. If it moves, the valve is operating properly. If it does not move, proceed to Step 5.


Disconnect Vacuum Hose

If the valve stem does not move in Step 4, disconnect the vacuum hose that is attached to the valve. While the engine is running, place the forefinger over the hose opening for a vacuuming pressure on the finger. If no pressure is felt, the valve controls will need to be checked.


Connect Vacuum Pump

Connecting a vacuum pump is necessary to check for clogs in the system’s hoses. While the hose is disconnected from the EGR valve, plug the hose with an object such as a golf tee to conduct the test. With the help of a friend, start the vehicle again. When the vehicle reaches normal operating temperature, connect the vacuum pump to the EGR valve. Apply up to 15 in-Hg of vacuum and observe the movement of the valve. If the valve moves, the engine will idle roughly or stall out. If neither occurs, the valve or passages will need a thorough cleaning. If the valve does not move at all, replacing the valve is necessary.


Shut Down Engine

Now that the issue has been discovered, shut off the engine and check the rest of the system for any broken or loosened elements. Once the valve is cleaned or replaced, re-install it back to the valve hose.

Following the steps above should have the vehicle running properly again. It may also be necessary to extend the EGR system test by spraying a carburetor cleaner on the diaphragm of the valve. The engine should continue to idle normally. If it does not, it is an indication to replace the EGR valve.