i have a lot of dumb questions... but some times i start my car and in neutral cold, it idles at about 1700 and other times i start it and its at about 900... then after driving idle is down to about 500... then if i turn it off for about 10 minutes and start it, the idle is back up to 1500 or somewhere around there. what could be happening?

 

Sounds perfectly normal to me. It will Idle higher when you first start it up to make sure oil and everything is pumped through the system. In a nut shell, the motor is "warming up." Once it's warmed up, it will drop down to around 500-700rpms, mine sits at 500 most the time.