Business Notes AUTOS

Since investors have lately lacked much confidence in General Motors, the company decided it was time for some major self-promotion. In a dramatic act to demonstrate GM's belief that its stock is undervalued, Chairman Roger Smith said the firm would buy up to 20% of its shares by the end of 1990. At current prices that would cost more than $5 billion, making the stock buyback the largest in corporate history. After the announcement, GM's stock spurted 3 7/8 points, to 79 1/2, before falling back a bit to finish the week at 77 7/ 8. The decision also sparked a general stock market rally, which sent the Dow Jones industrial average up 53.71 points to a record 2280.23. But the euphoria will soon fade unless GM revs up its sputtering business. Its car and truck sales so far in 1987 are down 28.4% from the same period a year ago.