Don't know for sure. Tell me what movie it is or go yourself to IMCDb.org and find the movie then it will list the cars that are in it.
I would guess a Pontiac or Plymouth.
Once the series started (Fall 1984), during the first season Detective Hunter drove a junker 1972 Chevrolet Impala with a brief view of a 1973 Chevrolet Impala that was painted to look like the 1972, a junker 1971 Chevrolet Nova, an old 1974 Plymouth Satellite, and a junker 1979 Chevrolet Caprice Classic. A 1971 Impala was actually shown exploding to end the episodes with the Chevrolet Impala. Monacos seemed to be the cop car of choice though, as second season saw Hunter occasionally driving a junker multi-side panel colored 1977 Dodge Monaco (jokingly referred to as the "Partridge Family" Monaco), a junker yellow '77 Dodge Monaco, a junker brown '77 Monaco, and an old black '77 Monaco. But the most popular, and famous Monaco was yet to come!