while at idle, about 1000rpm, then it surges to 1800rpm.
while driving about 25mph, l can feel slight accelleration and see the tach rise about 100rpm. Does anyone have any ideas?
also, AC is not blowing cool or cold at all.
by what I've read from all responses l turned off the AC and the idle is steady now.l live with no AC, besides it blows ambient temp air. Thanks for the great detective work.

You need to have a tech put it on the computer

You need a mechanic, but l think it is the compenstion sensor that kicks RPM up when the A/C comes on. It compensates for the load by increasing RPM. l will bet it is an A/C issue.

CHANGE THE THROTTLE POSITION SENSOR(it is not reading the position of the throttle at either idle or while driving )

there is no compensation switch for the a/c, it is done automatically by the engine computer on a cougar

But l do recommend the computer test with someone willing to work on the car (some mechanic shops wo not mess with a cougar) as it could be numerous things including a idle spped motor problem, a vaccum leak , a sensor concern as well as other things