wierd problem....

[lostmenoggin]

I have a wierd problem going on with my car. I frequently pass over the blue ridge mountains and when I'm going down the mountain I usually put the car in neutral and coast down. After I put it in N and started coasting the car slowly lost RPMS and just shut off. All the lights were still on, everything seemed to be working except the car just died. I put it in 5th and kicked the clutch and she started right up again. This ONLY happens when i'm coasting. When the car is just sitting and idling it doesnt shut off. Anyone got any ideas???? No vac leaks, wideband #s are looking good... I'm stumped..