Map Sensor Function, Bad Symptoms and Replacement Cost

Automobiles with internal combustion engines have something called an intake manifold. The function of an intake manifold is to manage the flow of air and fuel into the cylinders of the engine. This is an important job because the proper amount of air and fuel needs to enter each cylinder. That way, a successful combustion can take place and sustain the high-performance capabilities of the engine.

Basic Function

The engine also contains a sensory component called a MAP sensor. This is short for the manifold absolute pressure sensor. The function of the MAP sensor is to track the amount of manifold pressure that exists and then send this information to the engine control unit. This is the central computer which communicates with all the sensors of the vehicle.

Once it receives this MAP sensory information, the engine control unit will be able to figure out the air density and the air mass flow rate of the engine. By computing this information, the unit will know how much fuel needs to be injected into the cylinders of the chamber. That is how a good combustion can take place. It is dependent on all these sensors working together so that the engine control unit can manage the combustion process without any problems.

Bad Symptoms

If the MAP sensor were to ever malfunction, then it would create a weak engine combustion. You cannot operate your vehicle efficiently in this situation. The only thing you can do is have your MAP sensor replaced. But first, you need to confirm that you have a worn out or bad MAP sensor in the first place. You will be able to confirm this by paying attention to all the symptoms that will result from having a bad MAP Sensor.

Below are the top 6 symptoms of a bad map sensor to help you figure this out in your own situation.

1) Check Engine Warning Light

The engine control unit will know when you have a bad MAP sensor. When the sensor fails to give this computer the proper information, it will know something is wrong. For instance, if the crankshaft position sensor and throttle position sensor tell the engine control unit the engine is idle, it won’t make much sense to the unit if it detects a reduced engine vacuum at the same time. Any kind of strange behavior detected like this will result in the Check Engine warning light turning on.

2) Bad Fuel Efficiency

A bad MAP sensor causes more fuel to be injected into the engine cylinders than is needed. This means your engine is burning more fuel than necessary. As a result, it weakens your fuel economy and efficiency. Then you’ll be forced to make more trips to the gas station and pay more money for fuel.

3) Emissions Inspection Failure

Increased fuel consumption from a bad MAP sensor will cause more carbon emissions to get produced at a faster rate. If you live in a state which forces you to get emissions inspections every 6 months, do not expect to pass the inspection if you have a bad MAP sensor. The inspectors will be able to detect the excessive amounts of carbon emissions.

4) Weak Engine Performance

If the engine control unit detects a high vacuum amount, then it figures there is a low load on the engine. The unit will respond by reducing the amount of fuel that gets injected into the engine. Now, this might seem like a positive situation, but it is not. A bad MAP sensor can throw off the reading and cause it to be faulty. This means the engine really needs more fuel to produce the power that is being demanded of it. Since it won’t be able to generate this power, the performance of the engine will be weakened.

5) Acceleration Hesitation

Sometimes a bad MAP sensor can cause less fuel to enter your internal combustion chamber. You will know this is happening if you try to accelerate your vehicle after it has been in a stop position and you experience hesitation. If the MAP sensor is in really bad shape, the engine might stall altogether after you step on the gas pedal.

6) Trouble Starting Engine

Whether you have too much fuel or not enough fuel in your combustion chamber, this will make it difficult for you to start your engine. You will know for sure it is a MAP sensor issue if you must step on the gas pedal first before your car will start. That is not normal, and it is a clear sign that your MAP sensor needs to be replaced.

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Replacement Cost

You cannot leave a faulty MAP sensor in your vehicle if you want to continue driving safely. Therefore, you will need to go to your local auto mechanic and have them replace this part for you. The total replacement cost of a MAP sensor is going to be anywhere from $130 to $200. The part cost itself will be around $100 to $130 while the labor cost will be $30 to $70.

As you can see, most of the expense will be toward buying the new part. It does not take long to perform the replacement job if you know what you’re doing. That is why that cost is so much lower. Of course, the hourly rate of your auto mechanic will play a role in that as well. And, on top of those costs, there will be taxes and fees added on as well.

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