The Lilywhites had taken the lead through Daniel Johnson's 89th minute penalty at a time when both teams were down to 10 men - Liam Lindsay had walked for two yellow cards shortly before and then Sky Blues substitute Fankaty Dabo saw red for fouling Emil Riis to concede the penalty.
Johnson had to wait three minutes to take the penalty after two Coventry supporters ran on the pitch at different times.
He was ice cool from the spot, sending the keeper the wrong way.
Six minutes of stoppage-time was added, plenty of it due to the delay caused by the pitch invaders.
And the clock had ticked beyond that when Coventry substitute Fabio Taveres curled home a fine equaliser after North End had only partly dealt with a free-kick played into their box.
It was a real sickener and there was clashes on the touchline in the aftermath which saw Ryan Lowe and a member of the Coventry coaching staff both shown a yellow card.
North End had built their way into the game after an uncertain opening spell and Johnson's penalty looked set to give them another win on the road - one which you wouldn't have begrudged them,.
The North End side had shown one change from last Tuesday night's 0-0 draw with Nottingham Forest, Josh Earl replacing the injured Patrick Bauer.
It meant a return to the back three for Andrew Hughes after he had started the Forest game at wing-back, with Lindsay used in the middle of the back trio.
Coventry had by far the better of the opening 25 minutes or so, PNE unable to settle on the ball in that time and they struggled to contain the home side's movement.
Todd Kane's early cross from the right-wing was met by Viktor Gyokeres who sent a header over the bar, Gustavo Hamer later sending a shot straight into Daniel Iversen's gloves.
Earl and Lindsay were booked in the opening spell as North End were put on the back foot.
The visitors began to offer more going forward as the half went on and in the last quarter of an hour or so, were the stronger side.
In the 28th minute, Johnson slid a pass down the right hand side of the box to find the run of Ched Evans, the striker's shot on the angle touched away by Sky Blues goalkeeper Simon Moore diving to his right.
A good counter-attack from North End almost brought some joy five minutes before half-time, Johnson leading it and feeding a pass to Alan Browne.
The skipper moved forward down the middle and fed the ball to the supporting Evans to the left of him, Evans' left-foot shot tipped over by Moore.
North End went close twice in the first five minutes of the second half.
The first saw Evans lead a counter attack towards the Coventry half, his ball finding Cameron Archer on the edge of the box.,
Archer's first touch took him wide in the box, the striker lifting the ball back into the middle where Evans' downward header was pushed behind by the keeper.
Good work from Earl created the second, the wing-back coming off the left and feeding a low pass to Johnson 20 yards out.
DJ took a touch and aimed a low left-foot shot towards the bottom corner, Moore diving to tip it past the post.
During a decent patch of pressure, Archer sent a low shot wide, then Johnson's cross from the left found Evans in the middle but he put his header too close to Moore.
In the 66th minute Ben Whiteman's corner from the left was headed just wide of the far post by Lindsay.
North End's first sub of the afternoon saw Emil Riis replace Earl, that change seeing Johnson go to left wing-back with Archer dropping off behind Riis and Evans.
Another chance came PNE's way in the 74th minute, Archer's low shot across goal from the left side of the box parried by Moore with Brad Potts' follow-up blocked by a defender.
Things took a dramatic turn in the 84th minute when Lindsay was sent-off for a challenge on Gyokeres - it earning him a second yellow card followed by red.
But down to 10 men, Johnson led a counter-attack and played a superb through ball to release Riis on goal.
The Dane was tripped in the box by Dabo, referee Keith Stroud pointing to the spot and then pulling out his red card for a second time to dismiss the substitute.
After the first pitch invader had been rugby tackled by stewards, a second ran on and went for a run before jumping back into the crowd without being apprehended.
Johnson kept his cool though, stepping home to roll home the penalty, sparking wild celebrations among the 2,594 travelling fans.
That should have won it for North End but they were hit by a sucker punch in the seventh minute of stoppage-time.
A free-kick came into the box which PNE partly dealt with but Tavares - on a stoppage-time substitute, chased it to the far side of the box, turned inside and curled a shot over Iversen into the far top corner.
Coventry: Moore, Hyam, Rose, Clarke-Slater, Kane (Dabo 63) Sheaf, Hamer, Maatsen, O'Hare (Tavares 90), Waghorn (Bidwell 63), Gyokeres. Subs (not used): Wilson, McFadzean, Allen, Shipley.
PNE: Iversen, Van den Berg, Lindsay, Hughes, Whiteman, Potts, Browne, Johnson, Earl (Riis 73), Archer, (Diaby 90) Evans (Ledson 90). Subs (not used): Ripley, McCann, Rafferty, Sinclair.
Referee: Keith Stroud (Hampshire)
Attendance: 19,743 (2,594 PNE)