The hosts failed to dominate the Championship strugglers and the crowd grew tired of the uninspiring hoofball produced by Steve Cotterill's men with set-pieces providing Pompey's best chances to score.
The visitors may well have taken the lead in the first minute after a defence, that was missing Ricardo Rocha, were caught on the break but Eddie Johnson's angled drive flew narrowly wide.
Iain Hume looked lively for Phil Brown's men and he almost broke the deadlock when Aaron Mokoena slipped and allowed him to curl the ball past the far post.
The game descended into a boring, scrappy affair after a lively start with both teams guilty of playing the long ball that was never going to work. The only piece of quality play saw Joel Ward, in for the injured Liam Lawrence, fire straight at Iain Turner after a neat passing move.
That was until Pompey were caught on the break and Johnson provided a through ball for Hume who got away from Mokoena and slotted past Ashdown to give the visiting supporters hope of completing a great escape from relegation.
Those hopes looked to have been immediately dashed when Greg Halford's long throw was flicked on to David Cotterill at the far post who nodded the ball in, only for the celebrations to be cut short by the offside flag.
The second half was arguably even worse in quality than the first. Pompey created little whilst Ashdown did well to beat away Keith Treacy's shot. With the visitors on top, Steve Cotterill brought off namesake David and the unimpressive Mokoena for Kanu and Carl Dickinson.
The fans were bemused as to why Dave Kitson, who had been ineffective yet again, wasn't replaced and it was left to a defender to bring Pompey level.
Hayden Mullins' corner was met by a powerful header from Greg Halford to equalise and the Wolves loanee may well have had another from a later corner but the ball was cleared off the line.
Preston still looked for a winner that they so desperately needed as Ashdown did well to tip Hume's goalbound shot around the post. Pompey huffed and puffed with their overly direct style of play but the best chance was to come from David Nugent who couldn't score against his former club as his free kick sailed over the bar.
The referee finally brought an end to what was a dire and disappointing draw that had the typical "end of season" feel about it.
Some players will come under heavy criticism following that performance. Aaron Mokoena was sluggish and will take the majority of the blame for Preston's goal.
David Nugent, a free kick aside, wasn't effective against his former club once again and I can't remember Dave Kitson even having a shot on goal yesterday. His confidence has been shot to pieces since playing up front on his own and he really needs a strike partner to get the best out of him.
What disappointed me the most, and most other fans who in were attendance yesterday, were Steve Cotterill's tactics. Fans come to football games to be entertained, not to watch the ball high in the air for long periods of time.
We have players in our squad who are more than capable of playing good football along the ground, so why does our manager insist on playing the ball so direct?
And why bring on Kanu, a player who is so skilled with his feet, if all you're going to do is get the defence to bypass him with long balls to a striker in Kitson who isn't known for being a target man who can hold the ball up?
I'm hoping Steve Cotterill realises that the fans weren't impressed with the performance and will show more ambition when Coventry visit Fratton Park on Tuesday. Let's see a 4-4-2 formation and the ball being played on the grass, like it was meant to be.
Pompey Player Ratings
Jamie Ashdown: 8 - Some good saves to keep Pompey in it.
Ritchie De Laet: 5 - Struggled against his former club.
Greg Halford: 8 - Our biggest goal threat, which says it all really.
Aaron Mokoena: 4 - Sluggish showing.
Hermann Hreidarsson: 6 - Steady as always.
Jonathan Hogg: 5 - Seemed to struggle.
Hayden Mullins: 7 - One of his best performances of the season.
David Cotterill: 5 - Ineffective despite disallowed goal.
Joel Ward: 6 - Started brightly but faded as game went on.
David Nugent: 5 - Failed to shine against former club again.
Dave Kitson: 4 - No meaningful shots on target.
Substitutes
Darryl Flahavan
Carl Dickinson (Mokoena 59): 6 - Looked good when he came on.
Nadir Ciftci
Kanu (Cotterill 59): 5 - Ball passed him by.
Danny Webber (Nugent 88): N/A - Good to see him back on home turf.