Cleaning EGR valves will usually correct a problem with EGR flow characteristics that are below the computer's predetermined threshold. The check engine light usually signals a code for incorrect flow and can be erased once the flow has been reestablished.
All EGR valves use a pintle attached to a metal backing plate built in to the vacuum diaphragm. As vacuum is introduced above the vacuum diaphragm, the vacuum causes the diaphragm to rise, carrying the pintle with it. The higher the pintle rises, the more it uncovers the port to the intake manifold allowing ever increasing exhaust flow into the manifold.
If the EGR is not cleaned sufficiently, its ability to react to the vacuum introduction and allow incorrect flow management is diminished. If coking exists at the intake port on the manifold or under or around the pintle exhaust gases will be introduced at an idle. This causes a rough idle and stalling as a result.
The EGR should also be checked for a perforated rubber vacuum diaphragm. This will result in a vacuum leak and prevent operation of the EGR. A rough idle and stalling can be contributed to this condition as well. Use a vacuum pump and make sure that it holds a vacuum. A quick check is to use a vacuum from the manifold on a running engine. Just connect the vacuum line momentarily and watch if the engine changes rpm. At the same time the diaphragm can be felt to rise as the vacuum is connected. This condition demands replacement.
To clean the EGR valve, set the valve upside down with the pintle up. Fill the valve in the area of the pintle with carburetor cleaner. Allow it to sit for an hour. Place a finger in the bottom of the vacuum diaphragm and push up. Work it up and down to loosen the coking in the chamber. A small pocket screwdriver or similar device can be used to expedite the cleaning process around the pintle. Repeat this process until the pintle moves freely with no resistance and closes into its seat properly. Replace the EGR valve using a new gasket to prevent leaks.
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Finding the EGR valve location is actually quite simple. Just look for the flying saucer on a pedestal. |
How do I replace an EGR valve? The EGR valve needs to be replaced relatively frequently. Learn how. |
Read articles about EGR valve problems, EGR valve location and cleaning EGR valves. |
