Ford Motor Co. yesterday announced three separate recalls involving 135,600 cars and trucks for brake, fuel and emissions problems, and General Motors Corp. said that it has recalled 34,341 cars because a small plastic decoration under the hood has caused 20 engine fires.

Ford said it has notified some 2,200 owners of 1985-model Mustang, Capri, LTD and Marquis models to see their dealers for inspection and possible replacement of a power-brake booster that could crack and come apart, resulting in the loss of braking ability.

Ford said an additional 13,000 vehicles, built in a two-week period in April, are in transit to dealers or in unsold inventories and will be checked for the same problem.

Ford said the defective boosters were discovered by the manufacturer.

The company also recalled 1,400 of its 1985-model Ford Ranger four-wheel-drive trucks with 2.3-liter engines with electronic fuel injection to inspect and reroute a fuel supply tube running along the frame rail.

Ford said the nylon tubes could rub against the driveshaft and leak if they moved out of their installed positions and wore through.

Ford has received no reports of accidents or injuries in either recall.

In a third action, the automaker notified owners of 119,000 of its 1981-model passenger cars equipped with 4.2- and 5.0-liter engines to replace a choke mechanism and return emission levels to acceptable levels.

Models affected are certain 1981-made Fairmont, Zephyr, Granada, Cougar, Mustang, Capri, Thunderbird and Cougar XR-7 models.

Canadian and California cars are not affected, and the emissions problem should not affect vehicle operation, Ford said.

Earlier this month, Ford recalled 1981 models with the 2.3-liter engine for an emission repair involving the car's oxygen sensor.

The automaker said it would make all repairs and adjustments free of charge.

The GM recall involves 1985-model Chevrolet Cavaliers. A piece of plastic that reads "2.0 Liter Fuel Injected" can shake loose from its mounting on the air filter housing and fall onto hot engine parts such as the exhaust manifold, GM said.

Cars with sound insulation blankets attached to the underside of the hood weren't recalled because the blankets tend to hold the decoration in place, GM spokesman David Hudgens said. The affected cars were built between October 1984 and January 1985.

Recall letters were mailed in early April telling owners to remove the decoration and throw it away, Hudgens said. The recall wasn't made public, he said, because it involved a small number of recently produced cars "and we knew where all the owners were."

No injuries have been reported in connection with the fires, Hudgens said.