Eight minutes after the break, Sexton kicked his fourth goal but Machenaud's second three-pointer gave France a scent in the 54th minute.
Remarkably, they retain possession through 41 phases and into the 83rd minute, Johnny Sexton, who had missed a 63rd-minute penalty that was looking like a costly error, steps back into the pocket and launches a long-range drop kick towards the posts from behind the French 10-metre line.
What has compounded matters‚ especially for the teams from the Home Unions‚ is the fact that their top players were engaged in a gruelling tour of New Zealand with the British and Irish Lions in the middle of past year. "It's just disappointing to see two players going off with knee injuries under an HIA". France had used all their replacements and would not have been permitted to send Machenaud back on if a HIA was not required.
Sexton's 44-meter drop goal nearly three minutes into injury time stunned the Stade de France as the host thought it would prevail after a splendid late try by wing Teddy Thomas.
"It says a lot about the management and that we've got some good characters in the team because it looked like it might be deja vu".
Ireland do not have a great record in Paris, having won there only once in the last 18 years, including a narrow defeat two years ago.
France hooker Tolofua out of 6 Nations with neck injury
Ireland also failed to win their opener the previous year, when they were defending champions, while France, for all their woes, are built on an impressive domestic foundation. He was wincing, he was limping, he'd clearly hurt his knee in a collision.
With so many new faces and little preparation time, France could arguably claim a moral victory against the tournament favourites. Both times they were put down as HIA.
But Ireland defended ferociously and never allowed Les Bleus into their 22 meters. "It's massive for him, incredible", said the full-back.
Josh van der Flier is a major doubt for the Dublin encounter, after he suffered knee ligament damage during the victory in Paris.
France: G Palis; T Thomas, R Lamerat, H Chavancy, V Vakatawa; M Jalibert (A Belleau 29), M Machenaud (A Dupont 67); J Poirot (D Priso 55), G Guirado (A Pelissie 74), R Slimani (C Gomes Sa 55), A Iturria (P Gabrillagues 61), S Vahaamahina, W Lauret (M Tauleigne 67), K Gourdon.
England, the second-ranked team in the world behind the All Blacks, open their campaign against Italy in Rome tomorrow.
Trump to Withdraw Nomination of Climate Skeptic as Top Environmental Adviser
Tom Carper (D-Del.), the top Democrat on the Senate Environment and Public Works Committee, said in a statement late Saturday. Withdrawing White's name may clear the way for Senate consideration of other environmental nominees.