Check the FD return spring to make sure that neither the spring nor the tab it rests against is broken. Otherwise, you may have either (1) a grungy FD return spring or (2) friction somewhere in the cable run. The FD spring can be flushed out with your choice of solvent/cleaner (wd40, Clean Streak, GT85, etc...) and re-oiled. If it's not the spring, check to see if operating the shifter produces slack somewhere in the cable. If the cable becomes slack along the down tube, and the derailleur fails to move normally, the bottom bracket cable guide may be grungy or otherwise in poor enough condition that it prohibits the cable from moving smoothly along it. If you have brifters, a stray cable strand could possibly be snagging the interior of the cable housing. And if you have brifters, and you no longer get a positive *click* when shifting, you might have a shifter issue.