Introduction to Intake Manifold Pressure Sensors

In modern engines, the engine control module measures or calculates air flow through an air flow sensor or an intake manifold pressure sensor.Turbocharged engines may use both components, and naturally aspirated engines usually use one or the other.If the intake manifold pressure sensor is faulty or damaged, the control module and engine will not function properly. The engine can run smoothly by servicing and repairing this sensor.

How the intake manifold pressure sensor works

The engine's control module uses this sensor data to run related data calculations, such as engine load, injector pulses, and spark advance angle.When not in operation, the MAP sensor reads barometric pressure data.Since barometric pressure varies with weather and altitude, the control module calculates this "zero" point before the engine starts, from which to fine-tune spark and fuel injection.

At idle, intake air pressure is typically between 16-22 inches of mercury. Because this is below atmospheric pressure, air will rush into the intake.When the driver applies engine braking, the pressure can be as low as 10 inches of mercury.Under acceleration, however, an open throttle allows air to rush in faster, increasing intake pressure. At full throttle, intake pressure and atmospheric pressure are nearly equal.

Malfunction of intake manifold pressure sensor

Sensors can fail due to blockage or damage.Sometimes too much heat from the engine can rupture the electronics in the sensor or the vacuum line.If the sensor fails, the engine will not be able to accurately calculate the load, which means the air-fuel ratio will become too large or too small.

So how do you know if the intake manifold pressure sensor is faulty? Here are some caveats.

1. Poor fuel economy

If the data reading from the ECM is low, the engine may be under high load.So it injects more fuel and ignites earlier. This results in excessive fuel consumption, poor fuel economy, and possible explosions.

2. Lack of motivation

If the ECM's data reading is high, the engine load may be low.So it reduces fuel injection and retards ignition timing. On the one hand, fuel consumption will drop. That seems like a good thing, but if too little fuel is consumed, the engine may lack the power to accelerate and overtake.

3. Unqualified emission inspection

A malfunction of the sensor can lead to an increase in harmful emissions as fuel injection does not correspond to engine load. Too much fuel can lead to higher hydrocarbon and carbon monoxide emissions, while insufficient fuel can lead to higher NOx emissions.

4. Unstable idle speed

Insufficient fuel injection can starve the engine of fuel, idling erratically, and may even cause a certain cylinder to not work properly.

5. Difficulty starting

Likewise, a mixture that is too rich or too lean can make the engine difficult to start. If you can only start the engine with your foot on the gas pedal, there may be a problem with the intake manifold pressure sensor.

A functioning intake manifold pressure sensor is the key to the normal driving of the vehicle. If you suspect there may be a problem with the sensor, please check the following parts first.

1. Electrical

Check the connectors and wiring first. Connectors should be firmly connected and the pins should be clean and straight.Corroded or bent pins can cause signal problems from the intake manifold pressure sensor.Again, the wiring between the ECM and the sensor should be intact. Prevent short circuit or open circuit phenomenon.

2. Hose

Some intake manifold pressure sensors are connected to the intake manifold by hoses. Check that the hoses are connected and intact.Also, check the ports for carbon buildup or other debris that could clog the hose and cause the MAP sensor to perform poorly.

3. Sensors

If the sensor and intake manifold are connected to the correct circuit, use a scan tool or a voltmeter and vacuum gun to check. Measure the voltage under no vacuum and full vacuum. If the sensor's output data is incorrect, it's safe to say that you should replace the sensor.