This is just a hunch, but the EGR (Exhaust Recirculation Valve) opens and closes and they are spring loaded and they can carbon up and get stuck open. It is not usually hard to remove the EGR valve and inspect it and clean it. With it in your hand, you should be able to push in the center plunger and it should spring return closed.
Ken
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Tuesday, October 28th, 2008 AT 10:01 PM