McIlroy's late birdie keeps him on top at PGA
Rory McIlroy of Northern Ireland hits his tee shot on the 18th hole during the third round of the 96th PGA Championship at Valhalla Golf Club on August 9, 2014 in Louisville, Kentucky - by Warren Little
McIlroy, who won his third major title three weeks ago at the British Open, birdied three of the last four holes to fire a four-under par 67 and stand on 13-under 200 after 54 holes.
The 25-year-old from Northern Ireland will play with Wiesberger in the final group -- but with a dozen players within five shots of the lead, a dramatic back-nine shootout for the Wanamaker Trophy appears set for Sunday.
Players feasted on prime scoring conditions over the rain-softened 7,458-yard layout, with six different people claiming a share of the third-round lead at some stage in a wild day of attacking golf.
Wiesberger, whose only 72-hole finish in a major was a share of 64th at last year's British Open, birdied the last three holes to match the day's low round with a 65 to finish on 201.
The 28-year-old from Vienna sank a short birdie putt at 16 then put his approach at 17 six inches from the cup to set up another birdie and seize the lead at 11-under.
Seconds later, McIlroy rammed in a 20-foot birdie putt at the 15th to match Wiesberger on 11-under.
Then McIlroy put his approach two feet from the cup at 16 for his own birdie to reach 12-under.
Wiesberger answered by chipping from 70 feet to six inches from the cup to set up a birdie at the 18th that put him in the clubhouse at 12-under.
After parring 17, McIlroy dropped his third shot seven feet from the cup at 18 and sank the tension-packed putt to maintain the same margin with which he began the day.
Wiesberger missed the cut in this year's US and British Opens and the past two PGAs.
Rickie Fowler, this year's British and US Open runner-up, was third on 202 with five-time major champion Phil Mickelson another stroke adrift. Both Americans shot 67s Saturday.
Also on 203 was Australian Jason Day, whose third-round 69 included an escape from a greenside bunker to set up a birdie at 18.
A pack on 204 included 2010 British Open winner Louis Oosthuizen of South Africa, American Ryan Palmer, Finland's Mikko Ilonen and Sweden's fourth-ranked Henrik Stenson.