The Manifold Absolute Pressure (MAP) sensor measures the air pressure inside the intake manifold. This data allows the ECU to calculate air density and determine the engine’s load. For example, when you accelerate hard, the vacuum drops and pressure increases; the MAP sensor detects this instantly so the computer can add more fuel. It is crucial for ignition timing and fuel injection control. A faulty MAP sensor can lead to a rich fuel mixture, fouled spark plugs, and hesitation when the driver presses the gas pedal.