it can e a few things first your tps could be playing up second could be you idel control valve iscv it can be the litel blue sensor at tyhe back of the head that controls the idel iscv and the fueling first un plug the tps and see if it still does it not then change that if it make s no differnce then change the blue sensor at the back off head but un plug the iscv first that might be no good now