Japan's car exports to the United States for fiscal 1987, which ended last March, apparently fell short of a 2.3 million unit ceiling for the first time since Japanese car makers started voluntary shipment controls in 1981, industry sources reported Monday.

They predicted the trend is expected to continue this year, barring any major changes in the market situation.The top two automakers, Toyota and Nissan, said their motor vehicle sales on the U.S. market fell 15 percent and 21.7 percent respectively from a year ago.

Toyota's exports to the United States in fiscal 1987 totaled 873,508 units. Passenger cars accounted for 607,816 units, down 2 percent from a year ago.

Nissan's sales totaled 515,871 units, including 481,674 cars, down 11.5 percent.

The sources said shipments by all Japanese car makers in fiscal 1987 are down about 86,000 units or 3.7 percent from the annual limit of 2.3 million units.

Official statistics are scheduled to be announced later this month.

"Generally speaking, the Japanese makers suffered seriously from the steep appreciation of the yen against the dollar," said one official of the Japan Automobile Manufacturers' Association.

The official, who declined to be named, said "we expect the same situation to continue this year."