2002 Ford Thunderbird where is the idle air control located

i need to know where the idle air control is located on a3.0 ford ranger and how do i check to see if it is bad also what are any of the signs showing it is going bad there are no lights coming on like a check engine that i can use for any code i have had problems getting it started but somtimes the tac will almost go down to 0 and then will indle back up after a min. it cranks up fine after it starts only after it sits for a while it will give this problem it has 93000 miles on it and i have not had a tune up on it i have changed the gas filter and the coolent temperture sensor but this has not help at all its like when you try to crank it after it sits as if its not getting any gas