High RPMs on Start Up
 

Hey guys, I've got a 2001 3.8L Engine Automatic V6 Mustang Coupe, and I've had it for about 6 months. A few weeks ago, it started doing this thing where when i would start it up, the RPMs shot up to 2500. Then it would idle down to about 1500, 95% of the time. It went a way for a while, and it's started doing it again this week. When I switch it from park to reverse, then goes down to normal. Do you guys have any clue whats going on here?