The Sky Blues came from behind in an exhilarating contest to upset promotion favourites West Ham at Highfield Road.
The home side looked to have taken the lead after just 12 minutes when central defender Calum Davenport rose at the far post to meet a Michael Doyle free-kick.
The fans were jubilant and the scoreboard flashed 'goal' repeatedly, but referee Colin Webster ruled the 21-year-old - sought by Newcastle, Liverpool and Tottenham - had pushed his marker when jumping for the ball.
A shaky Hammers defence was again exposed on 34 minutes when Hayden Mullins collided with his own keeper causing the ball to run free. But Steve Staunton failed to capitalise with the goal begging.
However, it was West Ham who took the lead with just three minutes left to the break.
Nigel Reo-Coker weaved seamlessly through four Sky Blues players before slipping the ball to Teddy Sheringham, who tapped home from two yards out.
But the Sky Blues - with renewed confidence after their 4-1 win at Nottingham Forest on Saturday - hit back in injury time.
Rufus Brevett fouled the lively Andy Morrell on the edge of the box, allowing Michael Doyle to curl a glorious left-foot free-kick into the top corner.
A half-time rollicking from manager Alan Pardew was no doubt the spur for the visitors as they dominated the start of the second half.
Sheringham's close-range effort was superbly blocked by Davenport, while Luke Chadwick fired over from ten yards out.
But the Hammers were duly punished for their wayward shooting as Morrell crashed a thumping scissor-style volley beyond Stephen Bywater in the 72nd minute - his fourth goal in three games.
The chance was created by the impressive Doyle, who turned into space 30 yards out and swept the ball neatly into the path of the airborne striker.
Chadwick might have equalised for West Ham with three minutes remaining, but he smacked his first-time effort straight into the hands of Scott Shearer.
Steve Lomas added to the Hammers' misery when he was sent off for dissent in the dying seconds.