So what do you suppose a flow meter does? This is one of those automobile parts that is pretty self-explanatory in its name. A flow meter measures the air flow in an engine. Duh! In automobiles, the flow meter measures the amount of air going into the internal combustion engine. For sure, all electronically controlled diesel engines use a flow meter, and the flow meter gives measurements to the ECU, or electronic control unit, that little device that measures so many functions in your car.
By measuring the air flow the ECU then knows how much fuel is needed to inject into the cylinders. There are two types of flow meters. There is a vane flow meter that measures air volume and there is the hot wire flow meter that measures air speed.
Failure in a flow meter usually happens because they wear out; sometimes they will also fail and that usually happens when the flap or spring fails to operate properly. If this happens then the ECU will switch a warning light on and it will be time for maintenance. Oftentimes, if the flow meter wears out or fails to operate properly your engine will not idle properly or will die at idle.
In states where emission standards are regularly required, a failing flow meter will be cause to fail the emissions test and maintenance will be required in order to pass the emission test.
With all modern vehicles the failure of a flow meter is noticed by the ECU long before the car actually fails to idle. Thus another reason to pay close attention to that warning light when it comes on.
The ECU warning light, of course, can indicate failure or improper functioning for a number of parts in your car. The fuel pump is regulated by the ECU and sensors also provide information about transmissions, brakes, cooling systems and other functioning parts.
Unless you are a very handy mechanic the flow meter should be looked at by a qualified mechanic. In the old days this was a simple process; now, with the advent of the ECU, it usually requires expert assistance in determining which part is malfunctioning.
Used parts like the ECU and by extension the flow meter are always less expensive at a salvage yard. Check your owners manual for specifications and then shop with confidence at a reliable salvage yard for your used car parts.