I have a 2001 chevy malibu. had the oil changed a week ago. now today the car is ideling at 2 rpm, when i put it in drive it mad a cluncking noise. and now the gas gauge went from full to 1/4 tank, but then left it sit and started it back up , driving home it was at 2 rpms, didn't have to even it the gas, car just went. got home and now in park its at 3 rpms . and it won't idle down at all. HELP

Went out and started the car, still 3 rpms, white smoke coming out of tail pipe now, opened hood. don't hear anything, closed hood. heard like a popping noise, shut car off, and then noticed a wet spot on the right side front end. not oil, just wet, , restarted car, still at 3 rpms, battery light came on . and car shut off by itself. waited a minute and started it again, now its at between 0 and 1 rpms. sound like its running normal. pulled car up and then backed it in. then I noticed a small dot about the size of a quarter. when the tail pipe was when the white smoke was coming out. it was oil. shut car off , checked oil, its full , checked overflow tank for antifreeze still full. Now it seems to be idling ok. I don't know what to think now!!!!

No bubbles in the overflow tank, but now the problem is not all the time. one time you start the car, it idles at 2 or 3 , shut it off, restart it 2 or 3 times. and it idles like normal. or driving it, it runs fine, and then you pull up to park it. put it in park. and it starts to idle at 2 or higher again, and sometimes it won't idle down. or I'm driving it and slow down to go around a corner and all of a sudden it just idles back up to 2. I don't know how to check the throttle body or even where its located. Need some help, don't understand this at all.