New Zealand teenager Ko shot a four-over 75 to slump from 15th to 55th at the $US1.5 million ($A1.62 million) ShopRite LPGA Classic in Galloway.
She is one-over the card and 13 shots behind American leader Stacy Lewis with one round to play at the 54-hole tournament.
While world No.3 Ko has no hope of winning the tournament, she has at least maintained her remarkable record at professional tournaments, having never missed a cut.
She came very close on Saturday, shooting two birdies on her last two holes – the eighth and ninth – to climb above the cut line by one shot.
Earlier, the 17-year-old opened with four bogeys in her first six holes. She recovered slightly before a triple-bogey on the par-four fourth hole left her struggling to stay in the tournament.
Lewis leads by one shot from Christina Kim with a third American, Jennifer Johnson, another stroke back in third place on 10-under.