The Collaborative International Dictionary of English v.0.48:

Faultless \Fault"less\, a.
   Without fault; not defective or imperfect; free from blemish;
   free from incorrectness, vice, or offense; perfect; as, a
   faultless poem.
   [1913 Webster]

         Whoever thinks a faultless piece to see,
         Thinks what ne'er was, nor is, nor e'er shall be.
                                                  --Pope.

   Syn: Blameless; spotless; perfect. See Blameless. --
        Fault"less*ly, adv.-Fault"less*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

faultlessly
    adv 1: without a fault; in a faultless manner; "he solved all
           the problems faultlessly"