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EGR Servicing

Glossary

EGR valves are a common service item and chances are that by now most technicians have replaced quite a few for various reasons. Typically a technician will encounter a vehicle with a reported lack of power, smoking heavily or a check engine light on which are all difficult to verify sometimes without extensive road testing. Additionally, the PCM may also set several diagnostic trouble codes (DTC) such as P0401, P0404 with a code P2263 which almost always indicate that the valve is stuck, clogged or is sticking. Removal of the EGR valve for inspection might be the quickest diagnosis and replacing the valve is the only approved repair as cleaning is not always effective. Remember that there is also a position sensor inside the assembly that can also fail therefore it is important to always perform the EGR Position and Travel test. Many valves are removed looking similar to the valve pictured on the right with the upper port completely clogged with carbon deposits which cause the valve to stick. Since you already have the scan tool hooked-up and in Output State Control, you may also detect a lack of EGR flow by monitoring the IAT2 parameter while opening the EGR valve at a steady cruise on the highway. Normally, you should see about a 100°F increase in temperature. If no or very little temperature increase is observed and the valve position test passed, inspect for carbon fouling of the valve and ports.

Service the manifold too!
With higher mileage vehicles needing EGR servicing, it is becoming very important to inspect the valve bore and the EGR passages in the intake manifold. The edges act like filter collecting carbon, sometimes as thick as what is found in the valve itself. The picture at the lower left is an example of this carbon which has been partially broken up by removing the valve. Removing this build up and loose carbon will reopen the ports and restore the flow of EGR gasses. Additionally, a piece of that loose carbon might get into the valve and cause it to hang open causing a repeat repair. We found that the injector sleeve brush works perfectly for cleaning the bore and the build up on the edges. See the photo on the lower right. Rotating the brush on an angle is the key to scraping off the soft carbon. A small screwdriver or angled pick will also prove to be useful in this procedure. It is very important to inspect the passages! If the build-up extends deep into the EGR passages the intake manifold will have to come off for effective cleaning.

Always clean up.
After using the brush it is very important to remove all of that carbon that has been scraped and loosened from the manifold. Using a good vacuum is the only way to do this. Below left shows a Blue-Point Pneumatic vacuum being used so suck all of the loose carbon out of the intake manifold. We highly recommend this particular vacuum because of its power and hand held size which has proven to be quite effective. Whatever type of vacuum is used it must used with a tube or tool that can enter the EGR bore as shown in the photograph. Removing the EGR throttle or intake elbow will also allow for better access to the carbon under the EGR port. Most of this scraped off carbon will stay very localized and will be easy to vacuum up. Don't lose sleep over a few small bits because this is very soft carbon and it will quickly pass through the engine but do get as much as you can. Our experience shows that it all does come out easily. The picture on the right shows the desired end result with a clean bore and sealing surfaces with all carbon removed from the edges of the passages. The final step before installing the new EGR valve is to wipe the manifold clean with solvent or cleaner.

How to reduce the carbon build up? You can't eliminate it completely but there are things you can do to minimize it's accumulation. First, have your truck re flashed to the latest calibration. The most recent calibrations reduce EGR operation during extended idle periods. Extended idling is bad for diesel engines contrary to the "old mechanics tales." Use good quality fuel and drive it like you stole it! The intention of this article was to provide additional information and tips in diagnosing EGR and carbon related performance concerns and repairs. Further information on cooled EGR systems in diesel engines, please read the previously published article "Diesel EGR" which will further explain the system, it's components and it's purpose.

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