MAP Sensor Symptoms
by fixcars.net
A vehicle with a faulty manifold absolute pressure (MAP) sensor will usually display symptoms of a rough running engine during acceleration, deceleration or at idle.
The manifold absolute pressure (MAP) sensor is a common component on modern fuel injection engines that vaporize gasoline by pumping fuel into the engine under high pressure. The MAP sensor helps the engine determine its optimal combustion needs by calculating the mass of the air going into the engine, air temperature, and the rotations per minute of the engine. This allows the engine’s electronic control unit (ECU) to determine the density of the air flowing into the fuel mixture and the ECU can then adjust the both the air flow or fuel flow to maximize performance.
Although a vehicle will usually continue to run with a faulty MAP sensor, overall engine performance can suffer significantly and increased emissions are also a common side effect. Most normal car owners will not worry how their MAP sensors are working until the notorious “Check Engine” light comes on. When the engine’s computer sends out a diagnostic code indicating a malfunctioning MAP sensor is feeding incorrect readings to the engine it can suggest the vehicle may be running either "fuel rich" or "fuel poor," and both conditions are obviously not desirable and can eventually damage the engine. It is not uncommon for an engine code to incorrectly report a faulty MAP sensor due to simple vacuum leaks in a hose or port attached to the intake manifold. Fixing minor vacuum leaks can often solve MAP sensor problems and this means it is always a good idea to inspect all of the vacuum lines and hose attachments before replacing a sensor. A bad fuel pump or faulty exhaust gas recirculation valve can also cause MAP sensors to send out incorrect readings.
If the MAP sensor is faulty itself, the symptoms of rough running will often be the most noticeable during acceleration or slowing down, when there is the greatest difference between atmospheric pressure and the pressure inside the manifold. . Delayed acceleration followed by a sudden surge of power is a common sign of this condition. Another common symptom of a bad MAP sensor sending incorrect signals to the engine’s computer is an engine that runs very roughly or erratically at idle. Most modern cars today can be connected to a diagnostic code reading tool that will interpret the underlying causes and display codes indicating specific fuel/air mixture problems that will need to be addressed. MAP sensor problems can become especially important when a vehicle fails an emissions tests prior to its registration being renewed. When emissions’ testing detects an excess of exhaust emissions and other mechanical causes have been ruled out, the cause is usually a faulty MAP sensor that needs to be replaced.
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