Ford Motor Co. President Donald E. Petersen didn't stomp or shout. But he wanted to hear hallelujahs, which is why he was standing here at a lectern yesterday, shirt sleeves and all, talking about his company's born-again commitment to quality.

And he brought with him a witness, a Chicago assembly worker named Pierre Ashby who was laid off much of last year, but who came with Petersen to testify that Ford workers and managers were one in their commitment "to build the finest-quality cars in the world."

This was a revival meeting, folks -- the latest in a tour of 124 cities by Ford officials and factory workers who are trying to persuade a skeptical public that Ford means business when it says it has mended some previously shoddy ways.

The tour began Oct. 6 and ends Oct. 22. When it's all over, Petersen hopes the company will have converted enough people to increase Ford's current 17 percent share of the U.S. market to about 19 percent in 1983.

"We think we have our act together. We think we understand what we have to do," said Petersen, who added that he doesn't expect the public to buy Ford products on faith alone. No, sir.

Besides Ashby, Petersen brought along other witnesses: a snappy, red Ford Mustang convertible; a sassy Ford Thunderbird; a somewhat sedate Lincoln-Mercury Cougar; and several other 1983 models that cost Ford $3 billion to develop.

Whether Ford will get its money back on its new line of cars largely depends on the economy, Petersen said.

The economy has been devilish, sowing discontent and disaster in the marketplace with high interest rates and shocking car prices. Ford has been smitten by repeated declines in new-car sales, the latest of which was a 6.1 percent drop in September from a year earlier. That factors out to an annual decline of 13.3 percent from already low 1981 sales levels.

Meanwhile in New York, Ford Chairman Philip Caldwell told the New York Financial Writers Association yesterday that he is "mildly optimistic" that automobile sales have bottomed out, United Press International reported.

"Each month since June, sales at an annual rate have been slightly higher than the preceding month," Caldwell said. "That's not a long wheel base by any means but we shouldn't dismiss it."

Caldwell said there are several factors favoring better times for U.S. automakers in general, and Ford in particular.

"Inflation is down, interest rates are down and, for the first time since 1978, sticker prices are flat or falling," he said. In addition, "Gasoline prices are flat and there is ample supply."

"People are keeping cars longer and driving less," he said, but the demand has been stacking up. "Cars still wear out."

Petersen conceded that foreign manufacturers, particularly Japanese automakers, have had a better time of it, gaining more than 30 percent of the domestic market. But that isn't because the imports are more virtuous. And it certainly isn't because the imports have overall better quality, Petersen said.

"We still are in the process in this country of changing over from an array of large cars that used to be the right size" for the U.S. market, said Petersen, while the Japanese, for a number of reasons, have been building the new, smaller "right-size" cars for many years.

At that point, someone asked Ashby a question about salvation -- job salvation, that is. Ashby had worked at Ford's Chicago assembly plant 15 years. Last year, because of layoffs, he worked 27 weeks. The layoffs have made him and his surviving coworkers believers, he said.

"There's a feeling among employes that, in order to work more, we have to build a better car. . . . We're building a better car," Ashby said.