I have a 2003 Cavalier LS, today is went to my girlfriends house and I left my car running and went in to get her 2 min later I come out and my "trac control off" is on. I looked at it for a second and started to drive thinking that it would go off. As soon as I put my car in drive my car jerked forward with a loud thump. I put it in reverse and it did the same thing. I turned my a/c on the light went away and it stopped jerking but then my check engine light came on and then my "trac control off" light came back on and then my idle started bouncing from 1000 to 2000 rpms then my a/c would blow warm air at idle and cold air when driving. The car only has 27000 miles on it with a fresh oil change and replaced air filters. If anyone could possibly diagnose this PLEASE HELP.

sounds like its the IAT sensor. take the car to a local auto parts store and see what code it is throwing that would be my guess. when IAT sensor goes bad the car will idle funny any where from 500-1800 rpms and go back and forth and the a/c will sometimes work and sometimes not. thatd be my guess i could be wrong but def check to see what code it throwing. i know i had to replace mine 2 times already and a lot other people had to as well. mine is a 5spd but did the same thing and of course i dont have trac control but its prob making the computer think your tires are spinning when the rpms go up but the speed doesnt. good luck hope that helps