The car flowmeter: what it is, how it works, breakdowns and solutions

The flowmeter is a piece that is responsible for measuring the amount of air entering the engine and to send the data to the switchboard. Currently it can be found in diesel and gasoline vehicles, although not in all.

In this article we are going to tell you everything about this engine component. From operationUntil the most common faults, going through what you can do to clean or replace.

What is the flowmeter and what is it for?

The flowmeter is a sensor that measures the amount of air entering the engine, so that the control unit knows how much fuel to inject so that everything burns. Otherwise, a correct mixture between oxygen and fuel (stoichiometric mixture) would not be achieved. The correct ratio under ideal conditions for a gasoline engine is 14,7 grams of air for every gram of fuel (14,7/1).

Thanks to this, it is possible to burn the entire mixture to achieve good performance and efficiency, in addition to avoiding excessive emissions. Something that happens when the ratio between air and fuel is incorrect.

where is the flowmeter

It is normally located on the intake pipe, after the air filter. We can easily distinguish it since has an electrical connection which is responsible for sending the information regarding the amount of air that passes through the admission, to the engine control unit.

How does the flowmeter work?

The operation of current flowmeters is very simple. Count with one metal wire that is heated to a certain temperature and try to keep it constant. The more air passes, the more it tends to cool the thread and more electric current it needs to keep it warm. In this way there is a relationship between the amount of air and the electrical current, which is what the sensor uses to know how much air enters the engine.

However, its operation does not stop there, because changes in air temperature could alter the measurement. Air entering at 0ºC is not the same as at 40ºC, since the same amount of air would cool the thread more or less. That's why flowmeters also have a thermometer that adds the air temperature to the data and thus be able to offer an accurate measurement to the control unit.

The information sent by the flowmeter is analyzed by the engine control unit and, according to pre-established parameters, the fuel injected into the cylinders is adjusted for a better combustion. Thanks to this, fuel is also saved and pollution is reduced. Like the flowmeter, this operation also involves other sensors scattered around the engine that provide other relevant information.

Types of flowmeters

There are two types of flowmeters that differ in their operation, age, precision and reliability. These are:

• Butterfly: they were used in mechanical injection systems and worked thanks to moving parts. Hence they were larger and more susceptible to failure. They had a butterfly-type valve that opened more or less depending on the air that entered. The sensor knew the throttle position thanks to a variable resistor. This system is much less precise than the current ones.
• hot wire: used in electronic injection systems and therefore all passenger cars today. Its operation is the one described in the previous section.

Faults in the flowmeter

With no moving parts and very simple electronics, breakdowns in the flowmeter itself are very rare. These can come from a factory defect, from handling the flowmeter carelessly or from accumulated dirt that isolates the hot wire. Problems with the flowmeter are grouped into two:

• The flowmeter does not communicate with the control unit: in these cases either the cables have been disconnected at some point or the sensor has stopped working due to a defect or improper handling. Try to adjust the flowmeter and its connections well.
• The flowmeter gives incorrect values: in this case it is usually due to dirt insulating the wire. Here it may be a bad air filter that has let in dust, excessive pollution or rust from too much humidity or water. Furthermore, it is also easy to confuse an air leak with a faulty flowmeter. The control unit receives an amount of air measured by the flow meter, but then it reaches the engine less, because it leaves due to a leak in a joint or hose. Air can also leak out of a faulty EGR valve that does not close and leaves an open passage between exhaust and intake manifold.

In any case, the most common symptoms of this type of breakdown is that the engine light, abnormal noise at engine idle and irregular revolutions, more fuel cost, power loss y smoke of a different color. There are also cars that are difficult to start or do not even manage to start.

How to take care of it

The key parts to avoid causing breakdowns in the flowmeter are the air filter and engine oil. A quality air filter will prevent debris from entering stick to the hot wire.

As for the oil, you should know that the gases what produces are introduced in the intake to be burned and thus avoid a type of very harmful emissions. If the oil is very bad, these emissions can be detrimental to the flowmeter in the same way as the excess dirt mentioned above.

The next thing to keep in mind is that the less you touch the better. This way the connections will not be damaged and the cables will not lose contact anywhere. Needless to say, it is not advisable to clean the engine with pressurized water because you can damage a connection and water can enter where it should not, creating rust that will make the flowmeter stop working well. If you are going to clean the engine, do it as follows to avoid damage:

What happens if the flowmeter breaks?

In the event that the flowmeter fails, the control unit detects it and continues to work, but the normal thing in modern cars is that it goes into emergency mode. When driving, it will be noticed that the engine loses power and has a harder time responding. To be sure, it is advisable to go with the vehicle to the workshop, where they will diagnose us with the diagnosis machine if the flowmeter is really failing.

If you continue to circulate with a flowmeter in poor condition Major damage can be caused. An engine running with an incorrect air mixture generates emissions that can damage anti-pollution systems. In addition to the fact that it can generate more heat than it should, making other components suffer more, such as the head gasket, pistons and its segments.

Change or clean a flowmeter

Sometimes it's just a bad connection and it's enough to put it right back. However, if the problem is that it is dirty, you can try to clean with a product for air mass sensors. Even so, you should keep in mind that flowmeters usually have a self-cleaning function similar to that of modern domestic ovens, i.e. pyrolysis.

If the problem is another and you have to change it we can do it ourselves because It is very simple. We simply have to disconnect the electrical connector and remove it from the rest of the tube with the help of some keys. This task will take approximately a quarter of an hour or half an hour depending on the model.

Price of a flowmeter

If it is the flowmeter that is failing, it will be necessary to replace it with another, since it is a part that has no repair. The price of a new one can fluctuate wildly, as there are so many models. It usually ranges between 15 euros and 120 euros. Sometimes we can go to a spare parts house, where we can find it cheaper than in the official service.

Not all cars have a flowmeter

The information that the control unit must receive for the engine to work well is very extensive and comes from various sensors. So much so that there are cars that do not need a flowmeter because they get everything they need with others. For example, there are those that use a thermometer and pressure sensor (also called MAP).

In any case, the flowmeter It is a very common component. and can be found in most cars with heat engines. Mainly because it's cheap to manufacture and very reliable.