The world No 1 stormed into a four-shot lead on 18 under par after a remarkable 11-birdie effort at Quail Hollow, the scene of his maiden PGA Tour victory five years ago.
Following early gains at the third and fifth, McIlroy blitzed the Charlotte layout for nine birdies in 10 holes from the seventh, although he fell narrowly short of a magical 59 when he had to settle for pars at 17 and 18.
But his flawless round broke the course record he shared with Brendon de Jonge, and he was particularly pleased with another excellent display on the greens after struggling with the putter at last week’s Players Championship
“It was incredible, it was nice just to get on a run like that,” McIlroy told Sky Sports 4. “I felt like every shot I looked at, I was comfortable over it and I really putted well today, that was the thing that pleased me most.
“I rolled the ball really really nicely, and I don’t think I’ve rolled it like that in quite a while, so it was nice to see a lot of putts drop. And to break my own course record here is pretty nice.”
McIlroy will go into the final round with a four-stroke advantage over Webb Simpson, and he is a clear favourite to become the first two-time winner of the event as well as smash the tournament scoring record of 16 under set by Anthony Kim in 2008.
“More of the same on Sunday would be nice obviously,” he added. “But I just want to keep it going. Even though I’ve got a lead there’s no reason why I shouldn’t go out there and be aggressive and try make as many birdies as I can.
“I’m obviously playing well and I feel like this is a course where I can shoot another low score on.”
McIlroy admitted he entertained thoughts of a 59 when he stood on the 14th tee, but he was more than satisfied to have further consolidated his status as the world No 1.
“I looked at the scores in the morning and saw there were some low scores out there. I realised that early, got a little more aggressive, and it paid off,” he said. “I feel like the best player in the world and I wanted to go out there and prove that. But you never think that you’re going to go out and do something like that.
“I was thinking 59 from the 14th tee box, but obviously I’m delighted with the score. I guess I just have to forget about today – it’s a whole new challenge tomorrow.”