Colby Bishop scored a late penalty to ensure Pompey won at Port Vale to remain top of the League One table.
It was a dominant display from the visitors, but it looked as though they would be left frustrated in their search for a goal.
There were plenty of chances spurned, but Bishop kept his cool after Abu Kamara had been upended.
John Mousinho made a couple of changes from the side that won at Fleetwood the previous Saturday.
Myles Peart-Harris came straight into the starting line-up after arriving on loan from Brentford at the start of the week.
There was also a return for a fully-fit Connor Ogilvie, as Ryley Towler and ill skipper Marlon Pack made way.
Joe Rafferty’s continued absence with a neck injury saw midfielder Terry Devlin handed an unfamiliar right-back role.
The visitors looked a bit rusty at the start and Kamara had to scramble behind a dangerous ball into their box.
But Pompey soon settled and began to dominate the contest, with an attempt from Paddy Lane deflected behind by Jason Lowe.
Peart-Harris was looking particularly lively in an attacking role and saw a shot blocked after swapping passes with Devlin.
Ogilvie was next to go close, narrowly clearing the crossbar from the edge of the box after a corner had been cleared into his path.
There was plenty of pressure being applied and Gavin Massey was well placed to prevent a low Peart-Harris strike from entering the net on 25 minutes.
The chances kept coming and when Lane’s delivery was helped on by Bishop, the ball was fired over by Devlin from a tight angle.
Sean Raggett then did well to meet a Lane corner with a firm header, but it flew straight into the arms of Connor Ripley.
And another flag-kick was earned when Kamara’s low delivery from the left was sliced behind by a Valiants defender.
It was once again swung into the mixer by Lane and this time a header from Bishop was turned around the post by Ripley.
Half Time: Port Vale 0 Pompey 0
The visitors looked to pick up where they had left off following the restart and quickly had an opportunity to break the deadlock.
It was three-on-two as Peart-Harris drove forward and he elected to shoot himself, with Ripley getting down low to his left to make the save.
And the Valiants keeper came to rescue again just moments later, this time making a fine stop to deny Lane.
Mousinho freshened things up with a change just past the hour mark, as Ogilvie made way for Jack Sparkes.
The home side had rarely threatened going forward, although Tom Sang drilled a shot wide after a free-kick had ricocheted into his path.
And it had all started to fall a bit flat for the Blues, with the chances drying up as the second half progressed.
They slowly started to pick up again, though, and Alex Iacovitti had to turn behind a dangerous Lane delivery, while Tom Lowery also had a shot blocked.
Bishop then laid the ball off for Peart-Harris, whose effort bounced down into the turf and was tipped over by Ripley.
Josh Martin replaced Lane on 82 minutes, as the Blues kept pushing to find a way through the Valiants defence.
It was Kamara who soon had a chance to open the scoring, though, when Devlin cut the ball back for him in the box.
But the forward was unable to make a clean connection and his shot bobbled harmlessly past the post.
It looked as though time was going to run out for Pompey, only for Conor Grant to trip Kamara inside the box.
Referee Craig Hicks pointed straight to the spot, although there was a delay while he booked a member of the Valiants coaching team.
BISHOP kept his composure, however, and sent Ripley the wrong way to send the travelling fans wild with delight.
Unfortunately, that was also the cue for a moron from the crowd to run onto the pitch and try to confront the official, but he was intercepted and ejected from the ground.
Port Vale looked for a reply and a stoppage-time corner caused issues, but Pompey saw out the closing stages to secure a deserved three points.
Port Vale (3-4-1-2): Ripley; Lowe, Smith, Iacovitti; Massey, Weir, Gore (Sang 54), Grant; Chislett; Ikpeazu (Loft 39), Wilson (Shorrock 65)
Booked: Chislett, Iacovitti, Smith, Massey
Subs not used: Leutwiler, Debrah, Walters, Dipepa
Pompey (4-2-3-1): Norris; Devlin, Shaughnessy, Raggett, Ogilvie (Sparkes 61); Lowery, Morrell (c); Kamara, Peart-Harris, Lane (Martin 82); Bishop (Towler 90+3)
Goals: Bishop 88 (pen)
Booked: Lane, Lowery
Subs not used: Macey, Whyte, Scully, Saydee
Referee: Craig Hicks
Attendance: 8,068 (1,791 Pompey fans)