How to Detect a Faulty Manifold Pressure Sensor

January 27, 2012

A vehicle's manifold pressure sensor, or manifold absolute pressure sensor (MAP), is part of an engine's electronic control system. It's usually found in vehicles that use fuel injection. The manifold pressure sensor's function is to provide constant and instantaneous manifold pressure information to the car's computer, also known as the electronic control unit (ECU). The ECU uses the data to calculate density and determine the engine's air mass flow rate, which helps the computer determine the amount of fuel needed to create optimum combustion. When a vehicle has a faulty manifold air pressure sensor, many different engine problems can occur.

Symptoms of a Faulty Manifold Pressure Sensor
A faulty manifold pressure sensor has symptoms that closely resemble a vehicle with injector problems or low compression problems. Here are some of the most common symptoms associated with a faulty manifold pressure sensor:

  • A rich or lean fuel mixture. You may notice a gas smell after the engine has warmed up. The engine will knock or ping at times for no apparent reason
  • Excessive fuel consumption
  • A rough idle
  • Hesitation or slight jerking during acceleration, or when putting the vehicle into drive
  • The vehicle stalls or dies immediately after you try to give the engine gas to start the car moving

If you believe your vehicle has a faulty manifold pressure sensor, you should take it to a qualified mechanic so that complete engine diagnostics can be performed.

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