Class told in the end but Manchester City were given an almighty fight by Crewe Alexandra as the underdogs stunned their hosts by taking a shock lead after just 20 seconds.
Veteran keeper Peter Schmeichel could only palm out Rob Hulse's 20-yard snap-shot and alert striker Rodney Jack pounced to steer the rebound into the corner of the net.
City, fielding virtually their full-strength side, penned Crewe in their half for virtually the rest of the first period but could not force an equaliser, despite skipper Ali Benarbia twice hitting the woodwork.
He glanced a header from a Kevin Horlock free-kick onto the top of the bar after 24 minutes and then struck his own free-kick against the angle of post and bar just before half time.
A double substitution on the hour proved to be the catalyst for City's victory.
Darren Huckerby and Shaun Wright-Phillips replaced Shaun Goter and Lucien Mettomo and after Nicolas Anelka had hit the post in the 64th minute the Blues equalised five minutes later - thanks to Huckerby's pace.
He raced past three defenders on a solo run before being checked by Steve Foster on the edge of the area and as the ball ran loose Eyal Berkovic hit a first-time shot which was still rising as it hit the net.
A crazy spell of three goals in two minutes earned City a place in the third round draw.
They took the lead for the first time when Huckerby's low cross took a deflection off defender Richard Walker's heel and looped over keeper Clayton Ince into the net.
But Alex were level 60 seconds later when substitute Steve Jones squared the ball for Hulse to tap in from close range.
The jubilant away fans in their sold-out section had not finished celebrating, however, when that man Huckerby struck the winner.
Fellow substitute Wright-Phillips picked him out unmarked eight yards out and Huckerby lashed in an unstoppable shot.