The Washington Capitals won for the second time this exhibition season tonight, shutting out the sluggish Pittsburgh Penguins, 4-0.

Bobby Carpenter scored twice in the third period to ensure the victory, but all the Capitals really needed was Bengt Gustafsson's goal at 3:08 of the second. It was the first Capitals goal scored this exhibition season with both teams at five per side, a statistic that had bothered Coach Bryan Murray last week.

Gustafsson, set up by Milan Novy, slid the puck past Michel Dion. But Dion was replaced at the start of the final period by Michel Morisette, who didn't give the Penguins much help, giving up both Carpenter goals and another by Greg Theberge.

Neither team was very energetic in the first period, with a lot of end-to-end skating and passes that just missed. Pittsburgh managed only two shots that period, not even allowing Capital goalie Dave Parro to break a sweat.

The early highlight was a scuffle at the buzzer that kept both teams waltzing in confusion before heading for the dressing room. Pittsburgh's Gary Rissling, a former Capital, carried on a conversation with nearly everybody on the ice, but it was Washington's Dave Hutchison who began the following period in the penalty box. Later Rissling and Dennis Maruk continued the discussion and found themselves out for roughing.

Murray, who had complained last weekend of his team's lack of offense, seemed pleased by tonight's efforts. "We didn't finish up (plays and passes) very well," he said, "but I thought we got a lot more offensive chances."

But the Capitals' power play still has a power shortage, failing eight times out of eight against the Penguins, who had a zero-for-seven showing themselves.

Parro, in his first start of the season after a shoulder injury, was hesitant early, but smothered, kicked or flopped on the Penguins' 16 shots to prove he is back.

Pat Riggin will be in goal Saturday night when the Capitals play Pittsburgh again, in Johnstown, Pa., and he and Parro will split the shift for Sunday's game against the Penguins in Hershey . . . Defenseman Scott Stevens, who has been out with a hip pointer all week, is expected to play both weekend games.