start off this is not my car it’s my girlfriends but there’s been a coolant problem and she’s not the best on checking stuff (no hate to her) but yesterday she called me after a 30 min drive on the highway over passes and such and i think she over heated didn’t touch it tell today and it had no coolant in it so i checked the oil and there was no coolant in it but it’s puffing white smoke but not a lot but anyway now in park it revs up to roughly 3k and comes down to a little under 1k rpm constantly any thoughts or suggestions i was thinking idle air control valve but it’s also showing signs of a headgasket

 

You best pressure test this thing.