Check and clean you idol control valve.
You can clean it with carb. cleaner. Its
located on the top/back of your
manifold of the motor. Also it could be
a leaking vacuum m line. Most likely
one on the side under some other
hoses. Probably a elbow thats bigger on
one side than it is on the other. I wish I
knew the exact jargon language to tell
you but unfortunately a thing a majig
is the best I can do. I spent alot of
money and replaced alot of parts.
Hoping to get lucky. This sounds like
the icv and even if you have to replace it
its around $50. I replace the catalytic
converter, all my filters, and vacuum
hoses to the extent of approx. $2500.
My loss is your gain because I'm
sharing this with you. I believe in karma
so pay it forward. There is a video you
can Google that is spot on. Google ICV
on 2002 cougar. Or ask it my 2002
cougar is making a hooting sound.
Good lucK!