Challenger Edward M. Kennedy won his second consecutive squeaker over President Carter today, capturing 71 of Michigan's Democratic National Convention delegates to the president's 70.

With reports tabulated for 89 of 90 local caucuses around the state, Kennedy had 48.5 percent of the total vote, Carter 46 percent -- a margin slightly bigger than Kennedy's narrow win in last Tuesday's Pennsylvania primary.

Four percent of the voters chose "uncommitted," and 1 percent voted for other candidates.

Carter and Kennedy evenly split the 96 national convention delegates chosen today. But Kennedy's victory in the total vote should guarantee him a one-delegate edge when the state's remaining 45 delegates -- to be designated later by the state party -- are allocated between the two contenders.

This projection came from Massoglia Associates, a computer firm retained by the Democratic party to calculate the complex, weighted voting system used for today's caucuses.

In 1976, more than 700,000 Michigan Democrats voted in the presidential primary here and gave Carter a narrow victory over Rep. Morris Udall (D-Ariz.).

This year, though, the primary was replaced by a caucus system in which only 40,635 party activists were permitted to vote. About 16,000 of those eligible turned out today. That small group chose what will be the seventh largest delegation -- with 141 members -- to the August convention in New York.

The unique caucus system employed here that did away with secret ballots, one-man one vote and free access to the polls, tended to make local political loyalists more important than issues.

Accordingly, officials in both campaigns concluded this evening that today's vote could not be considered any kind of referendum on Carter's unsuccessful effort to rescue the American hostages in Tehran.

Kennedy campaigned in Michigan for one day, hitting hard at Carter's economic policies, which he said were responsible for the state's 11.3 percent unemployment rate and for the sharp decline in automobile sales. There was some campaigning by Carter surrogates.

But for the most part the campaigns were organizational efforts based on phone banks and mailings. The Carter camp appears to have spend about three times as much as Kennedy did.

Although the voting was close almost everywhere, Kennedy ran noticeably stronger in the Detroit suburbs, while Carter did well in rural areas. In the downtown Detroit caucus where Mayor Coleman Young, a Carter backer, and United Auto Workers President Douglas Fraser, a Kennedy backer, both voted, the candidates split the delegates evenly.

In the 16th Congressional District, a collection of industrial suburbs south and west of Detroit, the auto workers, teachers, public employes, and union officials eligible to vote gathered at the Kessey Ice Arena in Melvindale, hard by the Hot Strip Mill at Ford Motor's rouge plant, the massive manufacturing complex where Henry Ford perfected the assembly line 65 years ago.

The Carter volunteers won an early skirmish at the arena when they comandeered a room inside the front door for the "Carter hospitality center." There, arriving voters were treated to doughnuts, coffee, peanuts and reams of literature lauding the president.

The Kennedy camp, though, boasted the only celebrity campaigner on hand, Chris Kennedy Lawford, a tall, young man in sunglasses and designer cowboy boots who is the son of actor Peter Lawford and the nephew of the candidate.

The last-minute electioneering seemed futile, because the Democrats who turned out -- 792 of the 1,875 party members in the district are eligible -- had clearly made up their minds before today. About 95 percent of the voters were wearing buttons, either for Kennedy or for Carter, when they arrived.

"You're looking at a bunch of hardcore politicians," said Rudy Hickey of Ecorse, a hard-core Kennedy man. "They're interested in what they're going to get personally. They all cast their lot with one guy or the other months ago."

Thus there was no evidence that the attempted rescue of the Tehran hostages on Thursday had any impact on the voting at Melvindale. The incident intruded into the caucus only in the form of derisive jokes.

"It's a great day for Italians," quipped Mickey Guido, a city councilman from Dearborn. "Nobody can say Italy's got the worst army anymore."

Those helicopters they used have five gears," chimed Chip Dingell, son of the 16th's congressman, John Dingell. "Unfortunately, the only one operative was reverse."

There was no room or time, though, for serious debate or discussion. The participants lined up as soon as they arrived, signed their names on color-coded ballots (green for Carter, blue for Kennedy) and moved to the bleachers to await the results.

At 1 p.m., the doors of the arena were locked and a raffle was held to pass the time while ballots were counted. Finally, the district chairman strode to the center of the ice rink to announce the totals.

Carter got 404 votes, Kennedy 365, others 23. With 51 percent of the vote to 46 percent for Kennedy, Carter had won three of the five delegates the 16th district will send to the Democratic National Convention in New York. The 3-to-2 delegate split was exactly what most of the district's Democrats had been predicting.

It is sometimes said that the Kennedy-Carter contest will split the Democratic party. There were no signs of that at the 16th district caucus, though Kennedy and Carter partisans chatted and joked with each other and complimented one another for working hard.

The only anger surfaced when the Kennedy and Carter forces split into separate clumps in the bleachers to choose their respective delegates. The Carter backers got into a furious shouting match, marked by points of order and attempts to impeach the local Carter chairman, as they squabbled over which three of them would go to New York City in August.