if it ain't broke, fix it till it is

if it ain't broke

If something is going or working well, there's no need to change it. A shortening of "if it ain't broke, don't fix it," meaning the same. A: "We don't really need to implement these ridiculous changes, do we? Our current method is working just fine." B: "Sure, if it ain't broke, right?"
See also: broke, if

if it ain't broke, fix it till it is

An ironic expression intended to warn against damaging or ruining something that is perfectly fine by fiddling or interfering with it too much. A humorous play on the phrase "if it ain't broke, don't fix it." Of course the school board wants to change the grading system because if it ain’t broke, fix it till it is, right?
See also: fix, if, till
Farlex Dictionary of Idioms.

If it ain’t broke, fix it till it is

and IIABFITII
sent. & comp. abb. Don’t leave well enough alone.; Just keep tampering. (A play on If it ain’t broke, don’t fix it.) Does it work too well or something. You must say if it ain’t broke, fix it till it is. Leave well enough alone.
See also: fix, if, till
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • don't bet on it
  • Don’t make a federal case out of it!
  • a thing you don't want is dear at any price
  • don't get me wrong
  • don't give up the ship
  • don't beat a dead horse
  • all in (one's) head
  • don't cry before you are hurt
  • come it (with one)