engine question sohc

[EX-Svic]

while the car is in park after like 5 minutes it starts reving up and down from 1 to 1.5 i think and it stops only when i put it on drive or reverse . but after running out on the streets and i get home and put it on park it starts acting up again, Any idea whats going on with it ?? any advice is appreciated Thanks..........Peace

[EX-Svic]

could be one of those Thanks ill start cheking things on the list...........peace