Just recently my car has got this problem. Normally it would idle really high at start, even after the warm up, it would stay at like 1800 even if I left it for a while until I started driving, then it would have a normal idle at stoplights and such. Recently however sometimes when I start it up, it'll do the normal rev to 3k, then as it comes down, it goes under 1k and starts getting really low, and I have to keep giving it a little more gas so it doesn't start knocking and shut off. After this happens, I can drive fine and all, and I can idle fine until the car sits for a while again. Any suggestions? BTW - Its an 89' TII.