If you've noticed a dearth of bargains at your local car dealership lately -- no more rebates or zero-pecent financing -- congratulations. With the economy strong and consumers eager to spend, automakers have been able to ignore the kinds of promotions that had been cutting into the bottom line. The result: healthy profits. On Tuesday, Chrsyler Corp., the nation's third largest car manufacturer, reported third quarter profits of $651 million, a 54% gain from '93. Analysts expect similarly bouyant results in the coming days when General Motors and Ford report their own third quarter performances. Such positive showings, of course, are a mixed blessing for consumers, particularly those in the market for new wheels. Surging car sales reflect a vigorous economy, but fewer discounts on the dealer's lot.