The Envoromental Protection Agency ordered General Motors Corp yesterday to recall about 430,000 Pontiacs from the 1975 through 1978 model years to repair defective pollution-control equipment.

The EPA said a "poorly brazed joint" in one component can break under ordinary driving conditions, allowing excessive nitrous oxides to enter the atmosphere. Affected are Catalina, Bonneville, Firebird, Le Mans and Gran Prix models from 1975 with 455-cubic-inch engines, from 1976 with 350s, and from 1977 and 1978 with 350s or 400s.

The agency said the defective component, a transducer, was produced by Eaton Corp., and that about one million Ford Motor Co. and American Motors Corp. vehicles were recalled last year for repair of the same component.

Eaton since has redesigned the part, an EPA spokesman said.

On Friday, the Transportation Department announced that GM will recall 172,000 of its 1977 and 1978 Chevrolet Monzas, Pontiac Sunbirds and Oldsmobile Starfires because of a possible steering defect.

Only cars equipped with the L-4, 151-cubic-inch-displacement engine are involved in the action, according to the National Highway Traffic Safety Administration.

When the front suspension system in the cars in put under stress, such as when the car hits a bump or depression in the road and "bottoms out," therey may be a deformation to the left from engine mount support structure, the agency said.

"Over a period of time the effort required to steer the vehicle will be increased," the agency said.

Also, the Agriculture Department said a Wisconsin company is voluntarily recalling packages of salami after "several persons were reported to have become ill" from eating the products.

Officials said the recall was undertaken by Patrick Cudahy of Cudahy, Wis., and that it affects products under the labels of Patrick Cudahy, Pantry Pride, Weisel Usinger and Cohengenoa and hard salami.

Donald L. Houston of the department's Food Safety and Quality Service said the genoa and had salami products are "potentially dangerous" because they may contain a toxic substance-staphylococcal enterotoxin-that can cause food poisoning.