Mass Airflow Sensor Troubles

location of maf sensor

Mass airflow sensor problems can cause a variety of symptoms from the mildly annoying to the downright must repair type of issues. We'll discuss these in-depth on this page and show you a video on how to clean MAF sensors at the bottom.

A short list of some problems this senor can cause, but by no means all-inclusive would be a rough engine idle, a hesitation both mild or severe, a lack of power, poor fuel economy and yes a stalling condition. I should also mention the older the part is the more likley problems are. During the late 80's and through the 90's these air density measuring  devices where in a evolutionary stage.

In the early 90's GM was making some pretty bad MAF's. When I had a stalling complaint with no set codes I would do a very light tap test at the connector area and see if the RPM changed. If it did it needed a new one.

The mass airflow sensor can turn on the check engine light and set some strange codes depending on how poorly the car is running. I have seen random misfire codes and o2 sensor faults set. In many cases an engine light diagnosis can be narrowed down by the set trouble code. But often when the MAF sensor is malfunctioning some faults will actually be an after symptom of the root cause.

An example is a P0102, which stands for low air volume or input signal to the computer. This can be a wiring issue, problems with the sensor itself or even an actual air flow issue discussed further below.

This is why you still need to start with the basics and check for things that would be more common than a defective part. One of these would be a vacuum leak where air is being pulled into the intake manifold, in essence bypassing the flow sensing element.

Another situation where the mass airflow sensor can be bypassed is when the air duct that runs from the air filter housing assembly to the throttle body is torn. This is a very common condition on older high mileage vehicles and will also allow air to enter the engine that has not been counted by the computer. It can cause symptoms and set trouble faults that could indicate a sensor failure.

Contaminated Mass Airflow Sensor

If there is no vacuum leaks and the air induction hose isn't rotted, torn and verified to be in good shape it's possible that a dirty mass airflow sensor would display the same problems and symptoms as a defective or bad part.

Any vehicle with over 20,000 miles may experience problems due to contamination buildup on the heated element of the MAF sensor. As a rule of thumb the older the vehicle the more likely this problem would affect the operation of the automobile.

As an example in 1994 Ford came out with a technical service bulletin as well as Mazda that outlined the test procedure for a contaminated mass airflow sensor. Vehicle manufacturers eventually built in a self-cleaning mechanism into the sensor that would actually superheat the sensing element to burn off any contamination.

On older vehicles that don't have this function a cleaning will most likely be necessary at some point. A very important note that I learned the hard way! You should never use carburetor cleaner on a mass airflow sensor. It can ruin a good part.

The chemicals are just too harsh and can damage the plastic. This can cause more problems than the dirty sensor did. CRC makes a specialized cleaner that will remove any contaminants without damaging the plastic. There may be other manufacturers that make this cleaner but make sure they are plastic safe.

How a Mass Airflow Sensor Works

mass airflow sensor diagram

The sensor converts air flowing past a heat sensing element into an electrical signal that is provided as an input signal to the vehicle's main computer. The strength of the signal is determined by the energy needed to keep the element at a constant temperature above the incoming ambient air temperature.

As the volume and the density of air across this heated element changes the temperature of the element is affected and the current flow to the element is adjusted to maintain this constant temperature setting.

This method allows the computer to do an accurate analysis of the air that is entering the engine. Whether it is hot or dry, moist or cold and even a high or low pressure that would be affected by the altitude of the automobile can all be determined by this method.

The condition of the air that is entering the engine is extremely important because the denser the air the more oxygen it will contain. This is going to directly affect the air fuel mixture and the injector on time which will affect the emissions level and the fuel economy of the automobile.

If the element that is doing all of the sensing of the air becomes coated in contamination this will negatively affect the ability of the computer to analyze this all-important incoming airflow. Not only can a contaminated mass airflow sensor cause hesitation and stalling but it can also cause poor fuel economy and performance.

Even if cleaning the sensor does not solve all of your check engine light problems it might not be a waste of time. Opinions vary on how often you should clean the mass airflow sensor. Some mechanics will recommend the sensor be cleaned every time the air filter is replaced as regular maintenance. This is good when the right cleaner is used.

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How to clean mass air flow sensor video



BMW Mass Airflow Sensor

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