Car starts right up and then it starts to “hunt”. Hi,low,hi,low. Trying to drive,it will only go about 20mph with the throttle still going up and down. When I press the throttle to the floor, there is a small hesitation and the it takes off and is pretty smooth. As soon as I back off the throttle it starts to go up and down. Any ideas what this might be. The engine is a 3.6 v6. I’m need any help I can get. Thanks, Brad