Kevin Campbell threatened for the Baggies, stinging Jamie Ashdown's fingers with a shot from an acute angle, while Aliou Cisse drove wide for Pompey from 25 yards.
Iceland midfielder Sigurdsson was unfortunate eight minutes into the second half when his free-kick from 30 yards out came back off the post with JamieAshdown beaten.
Tyson hit the crossbar with a long-range effort in the 66th minute and McGugan curled a free-kick just wide before drawing a good save from JamieAshdown soon after.