EGR valves are especially prone to carbon buildup. The issue can be caused by dangerous fuel contamination, a lack of regular maintenance, and age, and it can lead to clogs that restrict the flow ...
The Family Handyman on MSN1y
How to Test and Clean an EGR Valve
The most common culprit is carbon buildup on the throttle body, exhaust gas recirculation (EGR) valve and idle air control ...