What type of derailleur does your bike have? Probably some Shimano model. Have you been turning the limit screws on the derailleur body or just the adjusting barrel? The barrel will control where the indexing stops points are. The limit screws will keep the derailleur from going too far in either direction, ie. they only impact the lowest low point and highest high point. Your problem sounds like an adjusting barrel issue. Note that sometimes a front derailleur can't make a proper shift or be used without scraping the chain in certain gear combinations that you shouldn't be using anyway (the cross-over gears). Try reading about front derailleur adjustment on parktool.com.
Oil is good, grease is better.
2007 Peter Mooney w/S&S couplers/Terry Butterfly
1993 Bridgestone MB-3/Avocet O2 Air 40W
1980 Columbus Frame with 1970 Campy parts
1954 Raleigh 3-speed/Brooks B72