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The MAP sensor (Manifold Absolute Pressure sensor) is a clever electronic sensor which measures air pressure in the engine's intake manifold which is used to determine the density of the airflow; the mass of air which is flowing through the car's engine. The MAP sensor has an important part to play in the performance, power and efficiency of the car's engine.
Normally located in the intake manifold, where the air is entering the vehicle, the MAP sensor will be encased in a plastic housing to protect it.
The engine needs the correct amount of air and fuel flowing through it in order for the fuel to burn in the cylinders and for the engine to ignite or spark at the right time. If the ignition sparks at the wrong time, there will be less power in the engine and it will try to make up for this by using more fuel, significantly reducing fuel efficiency, which in turn increases the car's CO2 emissions. If combustion occurs too soon this can also cause significant damage to various engine components. The MAP sensor detects the air pressure levels in the intake manifold and sends this information to the car's ECU (Engine Control Unit). Engine speed and air temperature are also constantly monitored by sensors which also send information to the ECU which is used, along with the data provided by the MAP sensor, to determine the amount of fuel flowing into the engine at the point at which the ignition sparks. The ECU uses data provided by the various sensors, to ensure the air and fuel mixture is correct in order for combustion to occur at the right point. Some fuel injection engines have a mass airflow sensor as well as or instead of a MAP sensor.
Prone to a build-up of dirt, oil and other unwanted deposits, the MAP sensor can get clogged up over time. When this happens, the performance of the engine is likely to be affected and engine emissions will be higher. A fault in the MAP sensor will cause the Check Engine light to show on the dashboard. A broken MAP sensor can sometimes prevent a car from idling properly (the ability for a car's engine to run while it is not moving) and may cause the engine to splutter and stall. If there is a fault in the MAP sensor a replacement MAP sensor is the ideal compatible replacement part.