Symptoms of a Faulty Manifold Absolute Pressure Sensor

Symptoms of a Faulty Manifold Absolute Pressure Sensor – The manifold absolute pressure sensor simply referred to as the MAP sensor is a vital component of a car’s engine system.

Since it is called a “map,” one might think this component is for navigation. However, the MAP sensor has nothing to do with directions or navigation. It is an engine component that measures the level of air pressure in the engine.

Its sole duty is to provide correct information concerning the flow of air into the intake manifold to the Engine Control Unit (ECU).

The ECU uses this pressure reading together with the engine’s RPM to ascertain the engine load, calculate air pressure, and adjust fuel pressure accordingly.

The sensors in a car wear out after some time and the MAP sensor is not an exception. After a long period of usage, a MAP sensor can wear out and start giving wrong data to the ECU, prompting the ECU to take erroneous actions that will affect the performance of your car.

When the manifold absolute pressure sensor is failing, it will begin to show some noticeable symptoms that will be highlighted later in this article.

Working Principle of the MAP Sensor

The working principle of the MAP sensor is less complex.

The sensor detects a load in the engine and sends a signal to the control unit. The control unit then uses this data to enhance the quantity of fuel in the engine, making the blend of fuel and air richer.

Enhancing the quantity of fuel and air will generate extra engine power that will be capable of sustaining the extra load.

The MAP sensor determines the density of air in the engine and when this information is transmitted to the control unit, the ECU calculates the quantity of fuel the injectors should release at that particular time.

The MAP sensor measures atmospheric pressure in the engine as 23.93 in Hg when the engine is off.

Atmospheric pressure varies depending on the weather. When the engine is idling, the pressure stays at 16-22 in Hg. At this point, the pressure in the engine is lower than the atmospheric pressure and will attract more air to get into the engine.

As the driver presses on the brake pedal, the pressure reduces to 10 in Hg.

When the driver accelerates, the throttle body opens up and lets in air faster to increase the engine’s pressure. This is where the MAP sensor comes in. It detects this increase in temperature and sends information to the ECU. The ECU then uses this information to calculate the engine’s load and the pulse of the fuel injectors.

Symptoms of a Faulty MAP Sensor

Just like any other component, a failed MAP sensor will affect the performance of your car and will exude several symptoms.

Such symptoms include:

Engine rough idling or stalling

A faulty MAP sensor can cause the air-fuel ratio in the engine to be too lean or rich. An unbalanced air-fuel mixture will cause a rough idle or lead to engine stalling.

Check engine light illuminates

A bad MAP sensor will send wrong signals to the engine control unit which will make the check engine light come on.

The ECU controls all sensors in the engine and will trigger the check engine light to illuminate if there is a problem with any of these sensors.

Lean air-fuel mixture

A failing MAP sensor can make the engine have a lean air-fuel mixture.

This happens because the MAP sensor is no longer able to measure the air pressure in the engine and does not send the right data to the engine control unit, leading to the release of an inadequate quantity of fuel by the fuel injectors.

A lean air-fuel mixture can knock down and destroy the engine.

Also, a lean air-fuel mixture will produce harmful emissions like carbon monoxide and nitrogen oxide and can affect the life expectancy of the engine.

Rich air-fuel mixture

A faulty MAP sensor can similarly cause the ECU to direct too much fuel and air to the engine, which will also lead to engine problems.

If the air-fuel mixture is too rich, the rate of carbon build-up will be faster. Again, the catalytic converter can clog, and fuel economy will be affected.

Engine misfiring

A faulty MAP sensor will lead to frequent engine misfires.

Since the engine is not getting the right quantity of air and fuel for combustion, the combustion process will be affected, and incomplete combustion will always lead to engine misfires.

Failed emissions test

Due to increased emission of harmful substances caused by a failed MAP sensor, your vehicle will fail the emissions test which can restrict you from driving in certain areas.

Hard starting

A faulty MAP sensor will make it difficult to start the engine.

This is because the car’s computer uses information from the MAP sensor to know the pressure of air in the engine and direct the right amount of fuel to the engine.

The wrong data sent to the computer by the MAP sensor will make the ECU deliver an insufficient amount of fuel to the engine, making it difficult to start the car.

Poor engine performance

A broken map sensor will cause a decline in the engine’s performance.

The engine is bound to misfire frequently, rough idle, and even stall which will make driving difficult.

How to Test and Diagnose a Faulty MAP Sensor

Before diagnosing a bad MAP sensor, you’ll need to carry out a preliminary check.

The MAP sensor is linked to other components in the engine, so the problem might be caused by another component other than the MAP sensor.

After inspecting other components like the intake manifold and vacuum hoses, you can now go ahead to test the MAP sensor.

Here is an easy guide to testing and diagnosing a faulty MAP sensor.

  1. Locate the MAP sensor in the engine compartment. If you can’t find this on your own, consult the car’s service manual for guidance.
  2. Inspect the vacuum hose and ensure it is connected properly to the MAP sensor and is not clogged with debris.
  3. Inspect the electrical wirings and other connections and ensure they are installed properly.
  4. Use an electronic cleaner to clean the MAP sensor and a diagnostic scanner to read the codes.
  5. Test the MAP sensor with a multimeter. If your sensor is digital, you can use a digital multimeter that measures frequency signals to test it.
  6. A faulty MAP sensor will throw the following error codes as P0068, P0109, P1106, and P1107 when you scan the car.
  7. Once you’ve tested and confirmed that the sensor is faulty, replace it with a new one.

Cost of Replacing a MAP Sensor

After testing and confirming that your MAP sensor is faulty, the next step should be changing it. Fortunately, the cost of replacing a MAP sensor is cheap and the procedure is easy. This means you can do it on your own without the services of a mechanic.

The MAP sensor will cost between $60 and $200. This variation in price can be a result of the model and make of your vehicle, or if you intend to purchase aftermarket products or OEM specifications.

If you do not have time to do it on your own, you can patronize an auto repair shop. This will cost you between $40 to $90.

Frequently Asked Questions

Where is the MAP sensor located?

The location of the MAP sensor in a car largely depends on the design or model of the car. In most cars, the MAP sensor is positioned on the intake manifold or a vacuum hose connected from the intake manifold to the car’s body. If you find it difficult to locate this component, you can always consult your car’s service manual.

Can I drive my car with a bad MAP Sensor?

No! A faulty MAP sensor can lead to issues like stalling, rough Idling, and misfiring. If you take the chance of driving your vehicle under these conditions, you are a step away from destroying your engine. Apart from engine damage, driving a car with a broken MAP sensor will be hazardous to the environment because of the increased carbon and nitrogen oxide emissions.

How can you tell if a MAP Sensor is bad?

If your MAP sensor is bad, you will notice some or all of the symptoms explained earlier. The check engine light will illuminate, and the dashboard will throw error codes, you will experience stalling, hard starting, and engine misfires. However, when you notice these signs, it is not okay to conclude it’s the MAP sensor because some other components can have similar symptoms. To confirm it is the MAP sensor, you should carry out a physical inspection and a test with a diagnostic tool.

Can a MAP sensor be cleaned?

Yes! A map sensor can be cleaned but this should be done with extra care to avoid damage to the sensor. The map sensor is located in the engine which means that it will easily get in contact with carbon, soot, and dirt. You should clean this off with an electrical cleaner.

How long do MAP sensors last?

Just like other sensors in a car, the MAP sensor is designed to last the lifespan of your car. However, the MAP sensor can fail after 70,000 miles. Sometimes, it can fail before this period due to other problems with the engine.