71–71–67 speaks to impressive stability in the debut for the 33-year-old Swede at Aronimink Golf Club outside Philadelphia.
Lindberg finished by going three under on holes 16 and 17 - an eagle followed by a birdie - and the round ended with a par, a nice three under on the admittedly difficult course.
Alex Norén also had a good day. He shot a 70 (par) and is at +4 heading into Sunday's final 18 holes in the year's second major. He rounded off Saturday's play with two late birdies.
Norén is tied for 68th.
"I'll try to put in a good round tomorrow. It's always about getting better," he told Viaplay.
The tournament is in full swing. Ludvig Åberg is three strokes under par after eight holes and is one of just over a dozen players in the lead.
Northern Irishman and US Masters winner Rory McIlroy played strongly and moved to the top of the leaderboard.
