MAP is an acronym for manifold absolute pressure. A MAP sensor is an electronic control that works in conjunction with the intake manifold, a system of tubes and chambers that carry a mixture of air and fuel to the intake valves.
A MAP sensor measures the pressure of the air channelled to the carburettor before it passes through the intake manifold. The signal that the MAP sensor emits changes in accordance to the pressure it detects.
Signals and Changes
The MAP sensor's signals helps the engine control module determine what changes need to be made in the fuel mixture. these changes include how much fuel is injected and when cylinders are ignited.
Importance of Readings
Without accurate readings from the MAP sensor the proper air-fuel mixture is not maintained. This has a direct effect on the performance of the engine.
Faulty MAP Sensors
If the MAP sensor malfunctions, the "Check Engine" light should come on, although it may not stay lit. Engine performance will be drastically reduced. One common performance issue is hesitation when attempting to accelerate. This is a result of the loss of horsepower that is characteristic of a vehicle has a bad MAP sensor.
Bad MAP sensors also contribute to an increase of auto emissions.