Clearly rattled, the American bogeyed the ninth as well after finding another bunker and Scott calmly made par to stretch his advantage to four.
Snedeker dropped further shots on 11 and 14 but rallied superbly with a birdie on the 16th and sank a 20-foot putt on the 18th to remain in contention for his first major title.
Woods recovered from bogeys at the first and third with a clutch of birdies at six, seven and nine to go to seven under.
A return to the metronomic golf which brought him two opening rounds of 67 led to five successive pars but a careless putt on the 15th green dropped him back to six under.
Els picked up two early shots to get to five under and after bogeying the 14th he made another birdie on 17 to stay in the hunt for a second Open title and fourth major.
World number one Luke Donald made an early birdie but took two shots to escape from a bunker next to the sixth green and the ensuing double-bogey stalled his progress and the Englishman carded a 71 to finish on one under.
World number two Rory McIlroy continued to struggle on the Lytham links with a scrappy 73 to finish five over and third-ranked Lee Westwood's wait for a major title will continue after his 71 left him at four over.
India's Anirban Lahiri caused the biggest cheer of the day with a hole-in-one, the first of the tournament, sending a nine-iron 150 yards into the cup.
"Just when I thought this experience was fantastic, it gets even better," said the 25-year-old after going round in 70 for a level-par total of 210.
(Editing by Tony Jimenez)