What Are The Symptoms Of A Bad MAP Sensor?

What are the symptoms of a bad MAP sensor

Many people are asking themselves: What are the symptoms of a bad MAP sensor? This is because they are suspecting that something is wrong with their car after certain signs arise.

Most common symptoms of a bad MAP sensor include engine check light is turned ON, harsh idle, delay or slowing down when accelerating. Other important signs can be thin air fuel mix, heavy air fuel mixture, misfires or not passed emissions inspection.

Before going through all the symptoms let’s find out a bit more about the MAP sensor and later on how can we clean it and test it.

What is the MAP sensor

The complete name of the MAP sensor is coming from Absolute Manifold Pressure Sensor.

The sensor has been used on the motor’s fuel utilization in electronic control units. The vehicles using a MAP sensor are actually fuel-injected.

The numerous pressure sensors provide a car’s electronic control device (ECU) with instantaneous pressure details. The results may be used to assess air volume and also to evaluate an engine’s air mass flow rate, which depends on the fuel metering required for best combustion.

A fuel-injected engine could use an additional sensor, called the MAF sensor, that is also known as a mass airflow sensor to monitor air intake.

The input of MAP sensor will be converted to air mass information using a process such as velocity concentration. Calculation of speed density will be accomplished with the rpm of the motor and also the heat of fuel.

Map Sensor Functioning Concept

The MAP sensor is an input detector that monitors the motor workload and generates a message that will be proportional to the amount of the vacuum. Afterwards, the engine device uses that information to alter the timing of the blast and boost power.

If the motor is running vigorously, the intake of the vacuum decreases owing it to the activation of the valve. The motor requires additional oxygen or even more fuel to hold the oxygen or fuel ratio consistent.

In reality, when the electronic control unit analyses the load signal from the sensor, it normally allows the fuel mix a little stronger than normal just so the motor can produce extra energy.

Equally, the software can hold up the timing of the explosion a little to avoid the spark that could damage the motor and its output. As requirements shift when the vehicle drives with a less light load, low capacity is expected from the engine.

The shock can not be opened excessively broad or it could be obstructed to increase the incoming vacuum.

The MAP sensor senses this and the software adjusts by trying to move out the fuel mixture to rising fuel usage and increases the ignition timing of the fuel efficiency out of the motor.

Symptoms of a bad MAP sensor

1. Engine check light is turned ON

Since your car has an OBD, it can light up the engine if it identifies an issue with the MAP sensor. Interpret the code auto service or at home if you possess a checking tool to decide whether the engine light is the result of a broken MAP sensor.

2. Harsh Idle

An incorrect air-fuel ratio can often induce unnecessary engine noise while sitting idle or hopping at idle stage.

3. Delay or slowing down

If you push an accelerator pedal to drive rapidly or jump out to overpass the other cars, you can find an engine block, delay, stumble that can be caused by a bad MAP sensor.

4. Thin Air Fuel Mix

If the air fuel blend is extremely thin, the effects could be much worse.

Thinner combustion becomes faster, and may degrade or reduce the lifetime of engine parts due to increased temperature in time. Thinner air-fuel mixtures may release many toxic pollutants, including nitrogen oxide and carbon monoxide. If knocking occurs during pressure, it may trigger a disastrous malfunction, destroying you the entire motor.

5. Heavy Air Fuel Mixture

When the air fuel blend becomes too heavy, the consequences can occur:

  • Spark plugs may be bad;
  • The fuel economy is going to drop;
  • The catalytic converter may well be stopped;
  • The exhaust can have a heavy scent of fuel;
  • Carbon reserves will accumulate quicker;

6. Misfires

When your own car will no longer produce the perfect blend of air fuel, it may be likely that your motor is unable to achieve full burning. If there is insufficient ignition, that can result in glitches. Often these issues will transmit the errors to the engine control unit.

Additionally, the ECU will turn on the check engine light in your cluster to inform you about the possible issues.

7. Refused Emissions Inspection

Whenever you stay in a place that allows you to experience a pollution check to authorize your car, a faulty MAP sensor is likely to provoke the car to malfunction due to the excessive concentration of toxic gases.

Can I drive my car with a bad map sensor?

The MAP sensor is perhaps the most critical fuel injection device in your vehicle.

When it’s start to get faulty, the ECU can transmit the inaccurate fuel / air ratio to the motor. Here either, it can offer low fuel efficiency and weak driving performance.

Under the worst scenario, it will wreck the engine by triggering the piston to blow up, damage the cylinders, break the bearings by infusing oil with fuel, as well as other unpleasant incidents. The MAP sensor is fairly cheap and is normally easy to repair.

Will a bad map sensor cause no start?

How to fix MAP sensor by cleaning it

  1. Position the vehicle on a level surface and let the motor calm down

    You have to remove the battery negative terminal once the motor is off.

    Seek a smooth surface to park your car to let the motor cool off for around 10 minutes. After that, lift the car’s hood.

    Prevent parking on the decline to be protected. Reach the motor gently to see if it’s cooled off. If it was still warm, hang for 5 more minutes or until it’s cold.

  2. Unplug the car battery for protection

    Search for the negative terminal of the battery. It is normally fitted with just a black cover.

    If not, there will be a minus sign above the terminal. Find the size of the torque socket that you will need.

    Connect this socket to your tool and detach the nut by rotating it left to right. Then remove the negative battery cable.

  3. Find the MAP sensor next to the intake manifold

    For most vehicles, the MAP sensor is positioned right beside the intake manifold. It will be connected to an electrical socket and is bound to a set of wires.

    There’s even going to be a flexible vacuum tube attached to it. When you have difficulty locating it, raise the wiring harness of the engine up to allow you a clearer view.

  4. Disconnect the vacuum hose

    You must cut the supporting circles to detach the vacuum pipe. Press the pins with each other to extend the circle and clear it off the hose. Continue this action till everything is clear and extracted. Then you will be able to unhook it.

  5. Disassemble all screws that bind the sensor on your car

    Normally there will be 2 or 3 screws connecting the sensor to the body. You can use the socket wrench to rotate it left to right and separate it from the engine. After that, the sensor will fall loose.

  6. Detach the electrical connection of the MAP sensor

    The connector is normally attached by using a clip to the MAP sensor. Usually, the clip can be unbuckled by slipping it up or down. Then keep the locking tab and disconnect the connection from the sensor. In case there is no clip, remove the electrical connection by holding the lock button and dragging it out of the MAP sensor.

  7. Spray the sensor with a cleaning product special made for it
  8. Retake all the steps back to mount it on its place

MAP sensor testing – How to test 4-wire MAP sensor

Usually a 4 wires MAP sensor has 2 wires for powering the sensor and 2 for outputting the signal. Here’s what you need to do:

  • disconnect the harness that is hooked up to the sensor;
  • set your digital multimeter on DC (20 V scale);
  • place the black probe to the negative terminal of the battery;
  • turn on the ignition, but don’t start the engine;
  • check all the pins from the connector harness and see where you get 5V or 12V – this will be sensor + ;
  • set the digital multimeter on Ohms (or diode/beep);
  • check the other remaining pins for the 0V – REMEMBER to not touch the other “+” pin that you just found;
  • the other 2 remaining pins will be the sensor output;
  • join back the harness to the connector;
  • try to use some clips or anything related to back probe the sensor in the output points;
  • set your multimeter on DC (20 V scale) again to read the values;
  • when you start your vehicle or when you accelerate it, the voltage should go up from the idling value of 0.9 – 1 V up;

I will leave you also a nice video if you prefer to have a visual aid:


When you ask yourself what are the symptoms of a bad MAP sensor you just found out that there can be many signs to indicate this. You should never ignore these signs and try to fix it as soon as possible. Then you will prevent further damage or unwanted issues.






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