Thanks for your input. Yep, I already removed the valve and cleaned it as best I can with Gumout and brake cleaner. As I said, the problem occurs when the throttle is closed and the engine dies. My understanding of the throttle plate sensor is that if it is not functioning, the engine idle would be too high, not too low. It seems like the engine is not getting enough air to keep running at low rpm under load and it stalls.