Trio share lead at tight LA Championship
Iwai revealed she had been in a rush to make her tee-time after her alarm clock failed to go off, but there was no sign of any fluster on the course.
She shot a bogey-free, eight-under round of 64, starting off her round with an eagle on the par-five first hole as the 22-year-old, who has six wins on the Japan Tour, put herself in contention for her first victory on the LPGA Tour.
Iwai was paired with her twin sister Chisato for the third round but said that hadn't influenced her approach to the day.
"There was no change of mind(set) because (she was) just another player, an opponent. But it was really fun. Really, really fun. A good experience," she said.
Coughlin, who claimed her first two wins on the LPGA Tour last year, was also bogey free as she shot a six-under 66, beginning her round with three birdies in a row.
"Only one bogey for the first three days, so that's always really good," said the American, after taking advantage of good conditions for low scoring.
"Made some really good par saves out there today and kind of in the middle of the round, when I kind of lost it there for a little while, was able to steady it and keep it going there at the end," she added.
Lingblad, who held a share of the lead heading into Saturday's action, was solid again with a four-under 68 as the tour rookie gave herself a chance of her maiden win on the LPGA circuit.
"I think (I) just need to stay in my own bubble a little bit, don't get too far ahead of myself," she said. "Obviously the goal is to win, but we can't win to tonight or on the first tee box tomorrow.
"So kind of just stay in the present and try to keep playing well," she added.
The leading trio are on 17-under for the tournament but there are plenty of players in contention for the title on Sunday with South Korea's Yoon I-na just two shots back after her eight-under round of 64.
American Nelly Korda, last year's Player of the Year with seven tournament wins, is a further shot back alongside Japan's Rio Takeda and Australia's Minjee Lee.
Korda, who defends her Chevron Championship title in the season's first major at Houston next week, made four bogeys on her round but also made eagle on the par-five 16th.
She was annoyed though to finish with her fourth bogey on the last hole to end with a five-under 67.
"Obviously a little upset with my last putt on the last hole. That's just really unfortunate. Other than that, I hit some really solid shots. Made some good putts too, but unfortunately did not make the last one. That stinks," she said.