How to Troubleshoot an EGR Valveby Edmund Gary
The exhaust gas recirculation (EGR) valve is the heart of the EGR system. The EGR valve allows small amounts of exhaust gases to be introduced into the intake manifold during moderate acceleration. The EGR valve is usually connected to the intake manifold. If the engine pings, has varying idle speeds without any change to the throttle position, idles roughly or fails an emissions test because of excess nitrous oxide, the EGR valve has a problem. The operation of the diaphragm of the EGR valve may need checking.
Increase the speed of the engine and insert a gloved finger in the underside of the EGR valve to feel for movement of the diaphragm. The diaphragm should move up (open) as the engine speed increases and move down (close) as the engine speed decreases. A slight vibration of the diaphragm plate is acceptable.
Check the condition of the vacuum hose if the diaphragm does not move. Disconnect the vacuum hose. Run the engine at 2000 revolutions per minute (rpm). Check for suction in the vacuum hose by placing one finger at the open end of the vacuum hose. If there is no suction, there may be a blockage in the hose or there may be loos fittings on one end of the hose.
Push the EGR diaphragm up with a screwdriver and release it. If the idle speed roughens, then returns to normal, the EGR valve is good. If not, the valve is faulty. Disconnect the vacuum hose and remove the bolts with a wrench. Remove the EGR valve and gasket from the engine.
Use a wire brush to clean off any carbon deposits. Connect a manual vacuum pump to the diaphragm and apply vacuum and release it. If the valve works smoothly, it can be used again. If the valve sticks, the valve must be replaced.
Install the cleaned EGR valve or a new valve on the engine with a new gasket. Tighten the bolts that fasten the valve to the engine. Reattach the vacuum hose.
- check It is best to study the hose routing of the EGR system before working. A decal with a diagram is usually placed in the engine bay on either side of the car. If it is faded, use a Polaroid Instamatic camera, like the One Step, to take a photo of the engine before you begin work.
- close Avoid getting close to moving parts while the engine is running, as injuries my result. Wear gloves while checking the movement of the EGR diaphragm to prevent burns. Set the parking brake and chock the wheels of the car to prevent unintended movement of the vehicle.
Items you will need
- photo_camera Thinkstock/Comstock/Getty Images