The N-2 Metrobus that pulled up at Bob Pierce's Cathedral Avenue apartment house yesterday morning had a wheelchair lift, as Pierce had requested. But when the driver tried to lower it to take Pierce and his wheelchair aboard, nothing happened. It was broken. Pierce smiled with resignation and rolled himself home.

Tony Young, a paralyzed Springfield resident, booked a lift-equipped bus on the 17 line for the trip to his Arlington office. But yesterday morning, he was not there to see if Metro had made good on its promise. Having misread a complex routing map, Young went to the wrong stop and missed the bus.

Both men were trying to use a new "on-call" plan that Metrobus inaugurated yesterday to accommodate riders who need lifts. It got off to an inauspicious start: Of the four people trying to use it, three did not ride for one reason or another, underlining problems the experimental plan presents both for Metro and the people who hope to use it.

The program does not offer door-to-door service, as has been tried in other cities for disabled riders. Instead, Metro promises to put a bus with a working lift on any specific trip in Metrobus' schedule, given 24 hours' notice. By calling 637-1825, patrons can reserve one-time or repeated rides. At the same time, lift-equipped buses are continuing to operate on 30 fixed routes.

The plan, the only one of its kind in the nation, according to Metro, is a compromise growing from the Reagan administration's decision to ease regulations that would have required 50 percent of Metro's rush-hour bus fleet to be lift-equipped by 1989.

Currently 130 buses, or less than 10 percent of the fleet, have lifts. With the devices costing $15,000 each, needing costly maintenance and prone to break down, Metro and other transit systems have complained that buying so many would be enormously expensive for the benefit gained.

Advocacy groups for the disabled disagree and continue to campaign for more lifts, and Metro plans to include lifts in 70 to 80 new buses it hopes to buy.

But, recognizing that funds are limited, the groups have worked closely with Metro to make the on-call approach succeed. The only major expense in the program is the salary of the person assigned to receive the on-call requests.

Metro officials acknowledge that poor maintenance in bus garages presents a major stumbling block to the plan. But yesterday morning, Metro says, buses with functioning lifts made three of the four special trips scheduled.

The only complaint of mechanical failure came from the bus dispatched for Pierce, the 57-year-old former head of the Disability Rights Center.

He had telephoned Metro on Friday to to book a wheelchair-lift bus. Metro confirmed that a lift bus would be on the N-2 leaving Friendship Heights at 11 a.m., with another for his return journey in the afternoon. He planned to transfer on Wisconsin Avenue and continue on to the Library of Congress.

The N-2 arrived on time. But driver H.I. Williams knew nothing of a special order. "They didn't tell me anything about it," he told Pierce politely. "I work this run every day." The bus did have a lift, however, which Williams tried to activate. "It's not working," Williams announced. He radioed for another bus.

Pierce told him not to bother. Waiting would make him miss his connection on Wisconsin Avenue. "I'll go back in and cancel the whole deal," Pierce said, "including the return trip. I've got a long drive tomorrow and I don't want to fool around."

Tony Young's experience illustrates the criticism that the on-call program gives disabled riders little flexibility and freedom, even if the buses do work. Because he was a few minutes late, Young's plans for the day were wiped out. A non-handicapped rider could simply have waited for another bus.

In addition to Pierce and Young, a Hyattsville woman trying to get to Bowie canceled her ride on an on-call bus after finding there was no elevator at the New Carrollton Metro station, where she had planned to transfer. The only successful handicapped rider was Bowie resident Richard Heddinger, who commuted to and from his job at the Energy Department on on-call buses.