Magic Johnson made two free throws with 17 seconds to play and Jamaal Wiles scored two with eight seconds remaining to lead the Los Angeles Lakers to a 128-123 victory over the San Antonio Spurs tonight and a sweep of their National Basketball Assoication Western Conference final playoff series, 4-0.

The Spurs' last chance to tie the game ended when Bob McAdoo intercepted Roger Phegley's inbounds pass with eight seconds left and scored on a breakaway layup.

McAdoo finished with 26 points. Johnson had 22, 11 in the fourth quarter, and Norm Nixon had 30 as the Lakers swept their second straight playoff series. They beat the Phoenix Suns in four games.

For the Spurs, Mike Mitchell scored 30-points.

San Antonio's George Gervin scored 38 points, but fouled out with six minutes to play and the Spurs trailing by three points.

As in the previous three games of this series, the Lakers took an early lead and the Spurs were left to play catch-us-if-you-can.

A 7-0 run, starting with a base line jumper by Wilkes and ending with a three-point play on the fast break by Nixon, helped give the Lakers a 13-7 advantage.

The Spurs chipped away and cut the advantage to 15-13 on a layup by Mitchell.

But the lakers pulled away aganin, this time on another 7-0 spurt--again started with a basket by Wilkes--and took a 22-13 lead.

Things really started looking bad for the Spurs when Gervin was called for his third foul with 5:41 left in the first quarter. He had only thre points at that stage of the game.

But Coach Stan Albeck left Gervin, the National Basketball Association's leading scorer, in the game and he warmed up scoring five more points the remainder of the period. The Lakers maintained their lead, however, mainly because McAdoo, a reserve, scored eight points in the last three minutes of the quarter to keep the lead at nine. Los Angeles led, 36-27, at the end of the first quarter.

The Spurs were't allowing the Lakers to get their fast break working the way it had been in earlier in the series, but whenever the Lakers did get out, they usually scored. On were on a two-onone break. While going full speed, Nixon lofted a 30-foot lob pass that Cooper grabbed two feet above the rim and slammed through the hoop.

Gervin went inside in the scond quarter and scored 10 points in the first three minutes of the period and the Spurs closed to 44-39. A three-point play by Dave Corzine and a layup by Gene Banks cut the lead to 49-46 two minutes later, but McAdoo took over again.

He scored on a base line jumper, then blocked two straight shots by Corzine. The sceond resulted in a fast-break basket for Nixon and a 53-46 Laker lead.

The Lakers got the lead to 62-54 with three minutes left in the falf on a fast-break basket by Johnson and two free throws by Mark Landsberger, but the Spurs outscored them, 10-4, the rest of the quarter to trail, 66-64, at intermission. Mike Bratz had four of the points for San Antonio.

Gervin finished the half with 22 points.

Whatever the Spurs did during the halftime intermission should havedone sooner, because they can out for the third quarter like a different team.

Outscoring the Lakers, 16-3, the Spurs turn the game around completely and took a 78-71 lead. They scored on their first eight possessions of the period as the Lakers foundered. Gervin had eight of those points.

After Johnson missed a jumper tp start the half, Gervin made a 22-footer to tie the score at 66. Kareem Abdul-Johnny Moore scored on a drive to give the Spurs a 68-66 lead.

A layup by Gervin and a follow of his own miss by Mitchell gave the Spurs their biggest lead of the game, 95-86, with 2:23 left in the period.

They didn't score again in the quarter, though.