Neither side got going in the first half in what was a scrappy game. Palace forced Lonergan into a couple of comfortbale saves but it was the visitors who looked more likely to score.
Irvine changed things at half time with Mellor and Neal coming on for Hawley and Whaley as the home team sharpened up. Preston's lack of goals has left them in danger of the drop and the closest they came was a Chris Brown close range header tha twas saved.
Palace stole the points with fifteen minutes remaining as Morrisson converted from two yards out from a corner. Preston were poor throughout the game and lacked any punch but stay out of the relegation zone but only just.