When I put car in park engine idles high for a few seconds then idles back down

It sounds, per your description, that the IAC ( idle air control ) motor may be lagging behind.
Usually a good throttle body cleaning will solve the issue. The motor over time is contaminated with combustion residue and becomes "sticky". I would recommend and thorough throttle body cleaning and a fuel injection cleaning. Both of which will improve fuel economy and idle stability.
Give it a try, you won't regret it.
Good luck.

Is the check engine light on??Could be a bad mass air flow sensor or throttle position sensor??? If the light is on take it by your local auto parts store and they will check the code for FREE and let you know what it could be.

Good luck !!!!!Hope this helps

Have the idle air control valve checked.