2000 Windstar. 3.8 v6. It is not starting and will not run until I tap a small gray Valve? on the top/front of the motor just under the opening of the hood. This valve is connected to the idle adjustment. I've been told there is a butterfly valve inside that is sticking. That has worked until today, now it is dead. What is this gray valve I've been beating on? How much should it cost to buy?

It's called an Air Idle Valve. It costs $80. It takes 5 minutes to fix with a 10mm wrench.