Why does my car rev high when I set cruise control and go on a slight incline? on 2002 Mercury Cougar

Whenever I drive and set my cruise control on, and go on even the slightest incline my cougar will rev up to 4000rpm. I have no idea why, please help!

Asked by for the 2002 Mercury Cougar
2 answers 1 comment
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When you set the cruise control the vehicle is trying to maintain the seed in which you set the cruise so when you go up an incline it want to go the spped you set it at but it needs more power to get up the hill. So the only thing the car can do is increse engine output to maintain the speed.
Well I know that but it used to not rev up like that until recently. It jumps up like 900rpm on almost flat surfaces now. It destroys my mpg now