Combine sugar, sour cream, syrup, and salt in a medium size heavy saucepan. Slowly bring to a boil, stirring constantly, until sugar dissolves. Cover and continue to cook 2 to 3 minutes to wash down sugar crystals from sides of pan. Uncover and cook, stirring occasionally, until mixture reaches soft ball stage (234°).
Remove from heat; stir in butter and vanilla. Beat with a wooden spoon until mixture is creamy and begins to thicken. Stir in pecans. Quickly drop candy by rounded tablespoonfuls onto waxed paper; let cool. Remove from waxed paper, and store in an airtight container.