Doyle tipped a drive from Wolves winger Matt Jarvis onto a post and then kept out the rebound header from Steven Fletcher.
Wolves striker Sylvan Ebanks-Blake had also been guilty of a glaring second half miss when he shot over with the goal at his mercy.
Both sides showed plenty of commitment and endeavour but the game was lacking in quality.
Defences were generally on top with centre-backs Curtis Davies (Blues) and Christophe Berra (Wolves) in commanding form.
Wolves winger Michael Kightly looked dangerous on his return to the side and on loan Blues midfielder Guirane N'Daw impressed.
But no one demonstrated the wherewithal needed to unlock the opposition until the late drama.
Neither side would have wanted a replay given their different goals for the second half of the campaign at league level.
Players and fans from both sides took part in a minute's applause for former Blues defender Gary Ablett, who spent three and a half seasons at St Andrew's, after his recent death.
Blues had the extra man in midfield, with Adam Rooney the lone striker, but there was little goalmouth action in the opening 45 minutes.
N'Daw did well to nick the ball away from Kevin Doyle after he had latched onto a pass from Ebanks-Blake inside the City box.
Wolves newcomer Eggert Jonsson flashed a 20 yard drive over the bar and a quick throw-in from Wade Elliott found Rooney inside the visitors area but Roger Johnson blocked his shot.
Jordon Mutch was only just too high with a shot on the turn from a Nathan Redmond cross as Blues started to take control.
Johnson, booed throughout by the City fans, went down clutching his ankle after falling awkwardly when winning the ball in the air when challenged by Rooney.
He was immediately substituted - after 36 minutes - by right-back Kevin Foley with Stearman reverting to centre-back while Karl Henry took over as skipper.
The first opening fell to Ebanks-Blake a minute later after Ward had found him in space.
But Doyle was alert and the ball cannoned off his challenge to safety.
Blues were forced into a change after 48 minutes with Liam Ridgewell clutching his back as he was replaced by Steven Caldwell who played under Mick McCarthy when he was manager of Sunderland.
Wolves looked sharper at the start of the second period and Ebanks-Blake flashed a shot across the box.
Then Ebanks-Blake squandered a golden chance to put Wolves ahead after 58 minutes.
Michael Kightly got to the byline before squaring the ball back to Ebanks-Blake who was unmarked 12 yards out. But he lent back and fired his shot over the bar.
Davies blocked a fierce attempt from Kightly who was impressing on his return to the side.
But the Birmingham defender became the first player to be yellow carded for bringing down Kevin Doyle on the edge of the box.
Henry scooped the free-kick in the air for Stephen Hunt but his volley was just too high.
Richard Stearman made a crucial block on a shot from Redmond as the game started to open up at both ends.
Rooney was booked for persistent fouling with seven minutes remaining and then Christophe Berra blocked an effort on the turn.
Wolves nearly snatched it at the death but Doyle produced his double save to deny both Jarvis and Fletcher.