High Rpm on 1996 Cadillac DeVille

I Have a 96 Cadi Deville the rpm runs very high when in gear i dont have to give it much gas it will take off. when park the idle can run upto over 4000 rpm i have to shut it off. sometimes i will pull the key out and restart and it will ide normally, but while driving it can idle real high and have to do the same thing over, Cant figer it out. Can you help Thanks.

Asked by for the 1996 Cadillac DeVille
This sounds like a dangerous situation. it is most likely your idle air control device. There should be a Check Engine Light/Service Engine Soon Light on, yes? Have your car scanned and the problem traced down. You could kill yourself and/or some one else!! Be careful!!!

I recommended that you have your car SCANNED first. Replacing parts with out a firm diagnosis usually does not fix the car. You need to have a good diagnostic scan first and foremost. Good Luck!
I Changed the Idle Air Control, And the Trottle Position sensor,and I still have the same problem,but now it sound like the trottle is stuck wide open. I cant drive it in its condition. From start up the Idle is up to 4000 + RPM, and yes the Service Engine light is on, I get a message to Service Emission. Thanks again for any information.