McAllister knows promotion is expected from his side, but the West Yorkshire club stayed outside the play-off frame despite leading with a brilliant first-time strike by Jonny Howson three minutes before the break.
Howson spun to volley home a cross from former Northampton midfielder Bradley Johnson, who was desperate to play a month after leaving Sixfields despite picking up an injury in training 24 hours earlier.
Northampton enjoyed the bulk of the first-half possession but missed their best chance when Jonathan Hayes drove a cross wide after good work down the right by Jason Crowe.
At the other end, Leeds should have gone ahead when top-scorer Jermaine Beckford raced clear but was denied by a telling foot from Brett Johnson.
The second half saw Northampton bring some much needed power to their frontline with the introduction of Akinfenwa and within two minutes of coming on he had muscled his way clear of the defence and produced a volley which screamed just wide of the target.
At the other end Beckford fired wide from 25 yards, but the home side drew level with 15 minutes left after Danny Jackman fed Poul Hubertz down the left and his slick delivery into the box was met by the substitute.
The result extended Northampton's unbeaten run to six matches - ironically stretching back to their 3-0 defeat at Leeds in early January.
Leeds are now without a victory in their last five league games, but at least they avoided the 2-1 defeat which was the outcome on the only previous occasion these sides had ever met in Northampton - during the Cobblers only ever season in Division One in 1965/66.