Nigel Pearson gave Howard his first start since October and the big Geordie rewarded his manager's faith with City's opener on eight minutes.
Matt Fryatt turned his marker on the right and put in a perfect cross for strike partner Howard to power in a close-range header.
Wednesday hit back with a Marcus Tudgay overhead kick which flew just wide.
But the momentum was with City, who doubled their lead on 25 minutes with a superbly executed goal.
A half cleared Richie Wellens free-kick was headed back by King to Fryatt, who again turned a defender, this time to create the space for King to carry the move on and score with a deft flick off the outside of his right boot from six yards.
Brian Laws' bid turn the blue tide with a double substitution with Jermaine Johnson and Darren Potter making way for Tom Soares and Michael Gray.
Wednesday struggled to the break without further mishap and after the restart almost pulled a goal back, but Tudgay saw his close range header beaten away by Chris Weale.
Then just before the hour mark, the Owls were denied again when Michael Morrison raced back to clear a Sean McAllister shot off the line after the midfielder had evaded a defender and rounded the keeper to give himself a clear view of the goal from 16 yards out.
Given their recent jitters City would have been grateful for the security of a third goal that almost arrived midway through the second half when first Howard and then Matty Oakley saw goalbound shots deflected narrowly wide.
But the Foxes did find themselves in the comfort zone on 74 minutes with a second strike from Wales international King.
Substitute full-back Ryan McGivern's cross was half cleared with a loose ball rolling off Howard to King, who joyfully side-footed home from 12 yards.
Howard's significant contribution to a much improved performance by the Foxes was acknowledged with a standing ovation minutes from the end when he was replaced by Yann Kermorgant.