My 2005 GT has a problem with the idle. In Park it just purrs like it is rising and falling. Does not stall but on the falling idle sound it sounds like it is going to. Can also hear it when driving, but again no stall issues.

Thinking maybe throttle body? Going to pull it off and clean it out. Also time for some fluid changes but I dont see that causing an idle issue.

I did put a new battery in about 2 months ago (roughly 150 miles ago). It has been sitting for this past winter aside from being warmed regularly. Any thoughts? Gonna hook up the tuner and check the codes tonight too. First time I've the car sit for a prolonged length of time without driving. (first winter snow after moving from florida. lol) Thanks!