Q: Loss of Power

Hello i bought a 2000 Toyota Celica from someone i asked when was the last tune up and they had no idea i check All the fluids however all was good it was missing a little engine oil so i refilled that but the Transmission fluid was really bad like it was super Dark i didnt have the money to buy a new filter and fluid so i drove with it like that for about two weeks this morning on my way to school i notice something unfamiliar like it was already losing power(it has a short ram air intake)which left like three hoses just hanging there it had a screw stuck on the vacuum hose i stopped half way and took it out it felt better i got to school coming back i start the car i didnt hit the gas to back up then when im going to take off i see the rmp go really high up but no speed it was like having the car in park and revving the engine ipushed it right back into the spot put the screw back on it worked after a while i changed the tranny liquid and filter Still no power when accelerating

My car has 188321 miles.
My car has an automatic transmission.