What was introduced in 1976 to help the onboard computer regulate the air/fuel ratio?

• A. The exhaust oxygen sensor.
• B. Three-way catalyst.
• C. Mass air flow sensor.
• D. Catalytic converter.

Answer: (A)

Closed-loop fuel regulation relies on feedback from the exhaust to tune the air/fuel mixture in real time. In 1976, the exhaust oxygen sensor was introduced to tell the onboard computer whether the combustion was producing too much or too little oxygen. With this signal, the ECU could adjust the fuel injector pulse width to keep the air/fuel ratio near the desired value, typically around stoichiometric for gasoline engines. This feedback loop dramatically improved emissions and fuel economy by moving from fixed fuel maps to responsive control. The catalytic converter and other components play supporting roles, but the key element that enabled regulation in that year is the exhaust oxygen sensor.