Change operating conditions, compare airflow and manifold pressure, and investigate a sensor reporting error.
Distinguish measured intake airflow (MAF) from intake manifold absolute pressure (MAP), predict their responses to throttle and RPM changes, and use modeled fuel trims to investigate an under-reporting MAF sensor.
Illustrative naturally aspirated, warm gasoline engine model. Values are invented for instruction, not OEM specifications. MAP is absolute pressure, not vacuum. Airflow depends on displacement, volumetric efficiency, temperature, altitude, and load; real fuel-control strategies and sensor responses vary.
A MAF-based system under-reports actual airflow. With credible oxygen-sensor feedback in closed loop, what fuel-trim direction would you generally expect?
Choose an answer and explain your reasoning.
The fuel-correction value is a steady-state teaching estimate, not a real-time STFT or LTFT PID. The MAP-based mode is an intentionally simplified speed-density approximation.
Compare readings at idle, cruise, and higher load. A MAF reporting error may create a fueling error on a MAF-based strategy, while a MAP reporting error may matter more when the ECM estimates air mass from manifold pressure. A post-MAF air leak can cause an idle-sensitive lean condition. Confirm suspected faults using OEM data and independent tests.