http://autorepair.about.com/library/...erms=EGR+valve
It's a common problem for EGR valves to stick. Fortunately they're easy to replace, but not necessarily cheap. It's also conceiveable (but less likely) that the EGR solenoid is sticking, busted, or disconnected. The EGR solenoid is what the ECU uses to control the vacuum signal to the EGR valve.
