McIlroy could only add a second round of 71 to his opening 65 at Southern Hills, despite being part of the early-late wave of players who enjoyed by far the best of the conditions over the first two days in Tulsa.
That left the four-time major winner five shots off the pace set by Will Zalatoris, who compiled a flawless 65 in the group ahead of McIlroy to enjoy a one-shot lead over Chile’s Mito Pereira, who returned a superb 64 in just his second major appearance.
Former champion Justin Thomas had set the early target on six under after battling the blustery conditions to card a second consecutive 67, with tournament officials opting not to cut the greens due to the forecast for winds to gust up to 40mph.
The same forecast also accurately predicted that the wind would die down in the afternoon, but it took McIlroy 12 holes to record his first – and only – birdie of the day as his bid for a first major victory since 2014 faltered.
Playing partner Woods, who won the 13th of his 15 majors the last time Southern Hills hosted the US PGA in 2007, looked set to miss the cut when he ran up a double bogey on the par-three 11th.
However, the 46-year-old – who suffered severe leg injuries in a car accident in February last year – rallied in typical fashion to play the remaining seven holes in two under to shoot 69 and make the cut with a shot to spare.
“It’s just unbelievable making the cut at Augusta and making the cut here,” McIlroy said of Woods.
“I was joking with Joey (La Cava, Woods’ caddie) saying he could have came back and played like Honda and Valspar, two of the flattest courses on Tour. It might have been a bit easier for him, but he comes to two of the toughest walks that we have.
“Just incredibly resilient and mentally tough. He’s feeling it on every swing, but to see what he did on that back nine; he missed a few iron shots but he got it up and down when he needed to.
“He’s the ultimate pro. Looking at him yesterday (Thursday), if that would have been me I would have been considering pulling out and just going home, but Tiger is different and he’s proved he’s different. It was just a monumental effort.”
As for his own game, McIlroy added: “I didn’t get off to the best of starts with the bogey on two and from there it was not really giving myself enough realistic chances for birdies.
“But those up and downs on 16, 17 and 18 I think were going to be really important. Just keeps me a little closer to the lead and doesn’t really feel like I’ve got such a mountain to climb if I had maybe dropped one or two over those last three holes.”
Two-time Masters champion Bubba Watson equalled the lowest score in US PGA history with a superb 63 to lie four shots off the lead, with England’s Matt Fitzpatrick another two strokes back despite admitting he is not a fan of the venue.
“My dad called me and he was asking how is the course looking and, no offence to the PGA here, but I was like, it’s a typical PGA, it’s long and tough and just not really my cup of tea,” Fitzpatrick said.
“(But) this year I’ve got a lot longer and it showed a lot the first two days with the clubs that I’ve been hitting into holes. Hopefully it’s a sign of things are changing a little bit for me and will open a few more doors on other golf courses.”
World number one and Masters champion Scottie Scheffler missed the cut after making a double bogey on his final hole to return a 75 and finish six over par.