Front Mech sticking

My shimano lx front mech has been clagged with grit and stuff and my cleaning regime has not been what it should. Result is that the front mech requires a little kick to drop it down the cogs. I’ve loosened it a little by cleaning and oiling and then a white grease coating. But it siezes up every day now. Has the spring weakened or can it be retrieved by an overhaul ?