why might my car have a high idle?

i've got a couple things going on here.

my car is a 1992 ford thunderbird v8 5.0L sport coupe. auto tranny.

first, when in ONLY park or neutral, my car has a very high idle. when in drive, it shifts perfectly, and idles at stop lights perfectly. but when i start it, it's up to about 1500rpm, when i park it slowly goes up to about 1800 or 1900 rpm in a controlled sort of way. like a smooth increase. reverse is also fine. i once tried at a long train to put the car in park--up to 1800rpm--tried neutral another time--same thing. it's NOT the pcv valve. we just replaced that a few months ago. my check engine light has never come on. my dad thought it had something to do with the air sensor, and after unplugging that with the car running, it idles low at 600 or 700rpm, and one time unplugging it, it stalled. and that unplugged is the only time the check engine light is on.

second, my car kind of drives itself. from a complete stop, it can get up to 3rd gear with me never touching the gas.