Woods, who led by one after an opening 67, burst out of a four-way tie on the front nine with back-to-back birdies from the sixth and pulled away from a late challenge by Briton Ross Fisher with three birdies to post 70 for a seven-under total of 137.
Five players were tied for second on three-under 141 -- holder Padraig Harrington of Ireland (73), two-time winner Vijay Singh of Fiji (72), US Open champion Lucas Glover (70), Australian Brendan Jones (70) and Briton Ross Fisher (68).
Fisher birdied three of four holes from the 14th to surge into a tie with Woods on five-under, but the 28-year-old Englishman bogeyed his last two holes to drop back.
On the front nine, big-hitting Spaniard Alvaro Quiros and Graeme McDowell of Britain joined Woods and Harrington in a four-way tie for the lead on four-under before giving way.
"It was a tough day all around," Woods told reporters. "The wind was blustery, the greens a little bumpy. A tough day."
Woods played some spectacular golf sandwiched inside a bogey start and bogey finish. He took five on the par-four first hole after driving into the left rough and lost a stroke to par after an errant approach on the l8th.
"I got off to a poor start and just kind of hung in there," said Woods, who is going after his 15th major crown. "Long way to go. Thirty-six more holes."
With winds gusting to 25 mph (40 kph) and firming up the massive greens that grew bumpier as the day progressed, Woods found another gear to leave his pursuers behind.
The 33-year-old, seeking a fifth PGA crown to match the record held by fellow Americans Jack Nicklaus and Walter Hagen, made three birdies in a row from the 14th.
Woods drove through the green at the par-four 14th, playing at a shortened 299 yards, and two-putted from 22 feet. At the the par-five 15th, he hit his second shot through the green, chipped up close and made another birdie.
At 16, he sank another 20-footer to bolster his lead. Woods came to the par-four 18th with a four-shot lead over Harrington, which he maintained as both players took bogey.
Jeev Milkha failed to break par for the second successive day but still managed to rise 21 places on the leaderboard for a share of the 48th spot after the halfway stage. The seasoned pro has a total of three-over 147.
Agencies
Scores (second round, US unless stated): 137: Tiger Woods (67, 70). 141: Vijay Singh (Fiji, 69, 72). Brendan Jones (Aus, 71, 70), Lucas Glover (71, 70), Ross Fisher (Bri, 73, 68), Padraig Harrington (Ire, 68, 73). 142: Ian Poulter (Bri, 72, 70), Lee Westwood (Bri, 70, 72). 143: Ernie Els (SA, 75, 68), Soren Kjeldsen (Den, 70, 73), Yang Yong-eun (SKor, 73, 70), Martin Kaymer (Ger, 73, 70); 144: John Merrick (72, 72), Grant Sturgeon (73, 71), Geoff Ogilvy (Aus, 71, 73), Tim Clark (SA, 76, 68), David Toms (69, 75).
