I just changed my oil and filter myself. I did NOT touch anything else in the process. The car was running perfectly before any of this. Anyway, after the oil change, everything was fine until about 5 miles down the road it started overheating. I let it cool down and proceeded the next 2 miles to my house. When I pulled into the drive way and put it in park, the rpms started revving up and down as if my foot was on the gas! I immediately turned it off, waited a few seconds and started it again. Still revving by itself!
I let it cool down, probably a half hour or so, and decided to put some water in it.
This time I started it and it was a normal start, no hesitation of any kind. I added some water and antifreeze and let it run about 20 minutes at idle, little smoke from somewhere other than the cap but shortly went away. No sign of a problem. I decided to drive to the grocery store about 3 miles away. Start it up, no problem, back out of the driveway and head down the road only to realize that the car is very sluggish, almost like the parking brake is on...it just won't go. About 2 miles out, the temp gauge spiked to red zone so I pulled over, NO SMOKE, no sign of overheating. And at idle it almost dies, I have to keep my foot on the gas and brake pedal at the same time. Can anyone explain to me what this could be? I have had this car forever and NEVER seen anything like this! I'm thinking the thermostat but I changed that a few months ago, also changed the top hose.
Someone mentioned a vacuum leak but I will say again, I touched nothing else!

 

How many miles are on it, which motor and tranny. Has the water pump ever been replaced?

edtheace