How to Troubleshoot a Car Engine EGR System

You might have noticed lately that your car engine is idling by itself before it gets warm or starts detonating when it gets warm. The engine is experiencing the symptoms of a bad Exhaust Gas Recirculation or EGR system. It is this systems job to recirculate certain amount of exhaust gases back into the intake manifold, at the appropriate time, to reduce nitrogen oxide emissions (NOx). If you are suspecting trouble with the EGR system in your car and have discarded other possibilities let's test the EGR system in your vehicle. You do not need special knowledge to run these tests.

Instructions

1

Open the hood of your vehicle and locate the EGR valve.

2

Trace every vacuum hose connected to the EGR valve and EGR system component. Make sure the hoses are not hardened, loose or broken. Damaged hoses leak vacuum or pressure and cause the EGR to fail.

3

Use your fingers. If the openings on the valve allow it-to push the stem up or down against the spring pressure to make sure it is not stuck. If the stem does not move, disconnect the valve using a wrench or ratchet. Clean the bottom of the valve and exhaust manifold passage from carbon residue that might be clogging the system. If the valve stem remains stuck, replace the valve.

4

Start the engine. Push the accelerator linkage with your hand to increase engine rpm to between 2000 and 3000 while watching the valve stem. If it does not move, disconnect the vacuum hose going to the EGR valve and place your finger on the hose tip. You should feel vacuum or pressure against your finger. If none of these conditions is present, inspect the valve controls.

5

Start the engine and let it reach operating temperature. With the engine idling, detach the vacuum hose from the EGR valve and plug it with a screw, Phillip screwdriver or golf tee. Connect a hand-operated vacuum to the valve-make sure the connections are clean and tight-and apply 15 in-Hg of vacuum as you watch the valve stem. As the stem moves, the engine should idle rough or stall. If it does not, the exhaust gas passages or the valve itself might be clogged. Remove the valve and clean the passages. If the valve stem does not move or the diaphragm does not hold vacuum, replace the EGR valve.

6

Start the engine. Using a can of carbutator cleaner, spray the valve diaphragm surface and listen for any changes in engine idle speed. If the engine rpm increases momentarily and drops every time you spray the diaphragm, replace the valve.

7

Check that wire connections for other EGR system components are not loose or broken.