The Blues’ home game with second-placed Cardiff City remains 0-0 at the break.
Town made five changes to the team which drew 1-1 at Carrow Road on Sunday with Joe Garner and David McGoldrick missing out through injury, and Martyn Waghorn dropping to the bench.
Manager Mick McCarthy stuck with the three-man backline of Cameron Carter-Vickers, skipper Luke Chambers and Adam Webster, while Jordan Spence returned at right wing-back for Dominic Iorfa, who dropped to the bench, and Jonas Knudsen continued on the left.
Cole Skuse was joined by Luke Hyam, making his first league start since May 2016, in midfield with Callum Connolly and Stephen Gleeson among the subs. Mustapha Carayol was a late withdrawal due to illness. Grant Ward, Bersant Celina and Freddie Sears formed a front three.
Cardiff made three changes to the team which beat Middlesbrough 1-0 at the weekend with Armand Traore and Callum Paterson missing out through injury, and Joe Bennett due to illness. Nathaniel Mendez-Laing, Matthew Connolly and Loic Damour came into the team. Ex-Blues keeper Brian Murphy was among their subs.
The Bluebirds might have gone ahead after a minute at a very quiet and noticeably empty Portman Road.
After Town had made heavy weather of clearing a corner, the ball fell to Connolly, who scuffed wide when he will feel he ought to have done better.
Marko Grujic shot over the top for the Bluebirds on 12 but chances were virtually non-existent in an opening 20 minutes in which the sides battled to gain the upper hand.
Town began to get on top as the game approached the 25-minute mark, Adam Webster nodding a right-wing Celina cross wide from beyond the far post.
The Blues went nearer to an opening goal on 27 when Sears cleverly fed Ward, who struck a low 20-yard shot which Cardiff keeper Neil Etheridge bundled past his left post.
Following the corner, Spence brought the ball back towards the area from deep before hitting an effort which was blocked and then unconvincingly cleared.
Hyam saw a shot deflect up into Philippines international Etheridge’s hands off Sol Bamba on 36.
A minute later the Blues went close again. Spence sent Sears away on the right and the former West Ham striker, who is without a goal in 30 matches, cut in and hit a shot which looked goal-bound until it deflected wide.
Town continued to look the more likely scorers playing the better football and in the 38th minute Spence flicked a header towards goal but without getting much power on it and Grujic cleared from in front of the line.
Cardiff were forced into a change in the 40th minute, skipper Sean Morrison making way for Greg Halford.
Three minutes later, Skuse played a deft ball into the path of Celina but the on-loan Manchester City’s man’s touch past the advancing Etheridge took the ball out of play.
Town were applauded off at the end of a half in which they had been the better side and had come closest to scoring through Sears, who was unfortunate to see his strike deflect wide.
The Blues had begun to get the upper hand midway through the half and were in control and passing the ball around with increasing confidence at the whistle.
Under-par Cardiff’s only significant chance came in the opening moments through Connolly with Bartosz Bialkowski in the Blues goal untested.
Town: Bialkowski, Spence, Chambers (c), Webster, Carter-Vickers, Knudsen, Ward, Skuse, Hyam, Celina, Sears. Unused: M Crowe, Waghorn, Bru, Kenlock, Gleeson, Iorfa, Connolly. "
Cardiff: Etheridge, Morrison (c) (Halford 40), Manga, Ralls, Zohore, Bamba, Connolly, Mendez-Laing, Damour, Grujic, Hoilett. Unused: Murphy, Feeney, Pilkington, Bryson, Wildschut, Madine. Referee: Andy Davies (Hampshire).