McIlroy, who won five times last year but has recorded just one top-three finish in 2013 since his controversial equipment change in January, looked set to miss his second major championship cut in succession.
The 24-year-old was five over par after 11 holes of his second round but birdied four of the next six to add a 71 to his opening 69 and finish level par, seven behind clubhouse leader Adam Scott.
"I was letting the round get away from me somewhat, but making four birdies on the last seven holes was nice to sort of redeem the round a little bit and keep myself in the tournament," said the world number three, who has been watching videos of his eight-shot triumph at Kiawah Island to gain inspiration.
"It makes me feel good because maybe in the middle of the season or a couple of months ago I wouldn't have been standing up here. I would have been going home.
"It's good to be able to do that and fight back and makes you feel good about yourself going into the weekend. Walking up the second hole, which was my 11th hole today [Friday], all I wanted to do is be here for the weekend. All of sudden, I'm somewhat back in the tournament.
"If I get off to a fast start tomorrow I'm right there."