Symptoms of a BAD/ Broken MAP Sensor

Symptoms of a BAD/ Broken MAP Sensor

In modern engines, the (ECM) engine control module  measures or calculates air flow via either a (MAF) mass air flow  or (MAP) manifold absolute pressure sensor. Turbocharged engines may use both, but naturally-aspirated engines typically use one or the other. If the MAP sensor is failing or broken, the ECM — and thus, the engine — can’t function properly. By maintaining and repairing your MAP sensor, you’ll keep your engine running smoothly.

MAP sensors fail by getting clogged, contaminated, or damaged. Sometimes, engine heat “overcooks” the MAP sensor’s electronics or cracks vacuum lines. If the MAP sensor goes bad, the ECM can’t accurately calculate engine load, which means the air-fuel ratio will become either too rich (more fuel) or too lean (less fuel).

So, Now hare we will know that our MAP sensor is going bad? Here are the key problems to look out for:

  • Poor Fuel Economy. If the ECM is reading low or no vacuum, it assumes the engine is at high load, so it dumps in more fuel and advances spark timing. This leads to excessive fuel consumption, poor fuel economy, and possibly detonation.
  • Lack of Power. If the ECM is reading high vacuum, it assumes the engine load is low, so it cuts fuel injection and retards spark timing. On the one hand, fuel consumption will go down, which seems like a good thing. However, if too little fuel is consumed, the engine may lack power for acceleration and passing.
  • Failed Emissions Inspection. Because fuel injection doesn’t correspond to engine load, a broken MAP sensor can lead to an increase in harmful emissions. Excessive fuel generates higher hydrocarbon (HC) and carbon monoxide (CO) emissions, while insufficient fuel may lead to higher nitrogen oxide (NOx) emissions.
  • Rough Idle. Insufficient fuel injection starves the engine for fuel, leading to rough idling and perhaps even random cylinder sisfing.
  • Hard Starting. Similarly, an excessively rich or lean mix makes the engine hard to start. If you can only start the engine when your foot is on the accelerator, you probably have a MAP sensor problem.
  • Hesitation or Stalling. When starting from a stop or trying a passing maneuver, stepping on the gas might not give you any joy, especially if the ECM is giving you a lean mixture based on faulty MAP sensor readings.
  •   Check Engline Light.Depending on the age of your vehicle, MAP sensor diagnostic trouble codes (DTC) may range from simple circuit, or sensor faults, to correlation, or range faults. A dead MAP sensor won’t read anything, while a failing MAP sensor might give the ECM data that makes no sense, such as low engine vacuum    when the throttle position sensor (TPS) and crankshaft position sensor (CKP) both show the engine at idle.


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