The DR Congo striker came off the bench to score the winner in the 74th minute with a powerful drive from the edge of the area.
Portsmouth are temporarily in charge of the Premiership table with 13 points, one ahead of second-placed Manchester United, who take on Arsenal on Sunday.
Elsewhere, Wigan came from behind twice to snatch a 2-2 draw with Everton at the Goodison Park.
In-form Andrew Johnson grabbed the lead for Everton in the 49th minute before Paul Scharner equalized for the visitors two minutes past the hour mark.
James Beattie put the Toffes ahead in the 66th minute from the penalty spot but Scharner leveled the score again just two minutes later.
In other matches, Reading beat Sheffield United 2-1 and Bolton Wanderers were held to a goalless draw with Middlesbrough.