Initial models were produced with carburetted four-cylinder petrol engines of 1.6 L, 1.8 L, and 2.0 L. Fuel-injection was introduced in late 1975 on the 320i – but in 1977, a carburetted inline 6-cylinder engine replaced both the 320 and 320i models,[5|new_window=true] while a detuned version of the four-cylinder injection went on sale in the United States. In 1978, the 3-series received its first fuel-injected six-cylinder in the 323i; and in 1981, a bottom end detuned 1.6 L was offered in the 315.

The cabriolet body style, manufactured by Baur, was produced from 1978 to 1981, with all available engines.

There was no BMW M3 model for the E21 generation, but several limited edition models were produced based on the model with the largest engine, the six-cylinder 323i.[6|new_window=true][7|new_window=true]

The E21 was replaced by the E30 3 Series in 1982.