1981 BMW 733i
6-cyl. 3210cc/174hp FI
With an experienced team and a lot of data.
In an effort to freshen an aging albeit pretty design, BMW introduced its E23 7-Series cars to replace the 3.0S/Bavaria in the U.S. in 1977. The 7-Series 730i was the flagship sedan version.
Designed by Paul Bracq, the 7-Series expertly echoed the 6’s design, only with four doors. Unfortunately, the 7-Series used a low compression head with air injection, exhaust gas recirculation (EGR), and thermal reactors to meet U.S. emissions regulations, which meant the cars were markedly slower than the European models. The EGR and thermal reactors also produced more heat than the 3.0-liter, 176-hp six-cylinder engines could handle, which caused cracked cylinder head and warping.
Beginning in 1980, BMW introduced a Bosch oxygen sensor and a catalytic converter, which solved the car’s heat problems. In 1983, Bosch L-Jetronic injection was switched to Motronic, which was much more efficient.
In 1985, the engine size was increased to 3.4 liters and the model was renamed the 735i respectively. The boost in displacement resulted in 6 more hp and 19 lb-ft of additional torque. A front air dam made the cars look sportier, and more equipment became standard. A more luxurious L7 was available, as well.
Neglected E23 7-Series are easy to find, as their well-equipped and sophisticated set-up meant that standard repairs were often expensive. Today these cars are best to be avoided, as they will ultimately cost more in the long run. Earlier cars, due to their EGRs and thermal reactors, are usually last on the list for enthusiasts. As with any older car, be mindful of rust, and check with a mechanic before spending more than you can afford to lose.