Troubleshooting an EGR valve

Given the different types of EGR valves, it is always best to follow the troubleshooting procedures detailed in the service manual, however, there are a few generic steps that can help to pinpoint diagnosis:

· Read any fault codes on electronically controlled EGR valves using a diagnostic tool.

· Check that all vacuum lines and electrical connections are connected and positioned correctly.

· Use a vacuum gauge to check the vacuum supply hose for vacuum at 2000 to 2500 rpm. No vacuum at normal operating temperatures would suggest a loose hose, a blocked or faulty ported vacuum switch or solenoid or a faulty vacuum amplifier/pump.

· Check the vacuum solenoid while engine is running. On electronically controlled EGR valves, activate the solenoid with a scan tool and check the vacuum at end of pipe. If the solenoid does not open when energized, is stuck in the open or closed position or has a corroded electrical connection, loose wire or bad ground, EGR operation will be affected. Identify the root cause before replacing.

· If possible, check the movement of the valve stem at 1500 to 2000 rpm. The valve stem should move if the valve is functioning correctly – if not, and there’s vacuum, there’s a fault.

· Apply vacuum directly to the EGR valve using either a hand vacuum pump or scan tool depending on the type of EGR valve. If there is no change in idle quality, then either the EGR valve is faulty or the passages are completely restricted. If the engine idles rough or stalls, the problem is being caused by a malfunctioning control system.

· Remove the EGR valve and check for carbon build up. Where possible, remove any carbon, being careful not to contaminate the diaphragm.

· Inspect the EGR passageway in the manifold for clogging and clean if required.