A vehicle's mass airflow sensor, or MAF, is the component that measures the flow and density of the air flowing into the combustion chamber. It helps the car's computer regulate the ratio of air to fuel. It's a critical engine performance component, so if it fails or begins to fail, you should have it replaced immediately.
Check Engine Light
The most reliable early symptom of a failing or failed MAF is the illumination of the check engine light on the instrument panel. Many types of problems may cause this light to come on, so you must have your car's computer analysed to see if the light is related to the mass airflow sensor.
An auto mechanic can analyse a car's computer for a fee, or you can do it yourself using a digital auto diagnostics scanner. These scanners are available at most auto parts stores, and though they all work a little differently, they're generally designed to be plugged into the car's circuit box so that they can read the computer data. After the scan, the scanner will display one or more numeric codes, which must be looked up in a reference book that accompanies the scanner. If you do this and the scanner codes refer to a malfunctioning MAF, you will need to have the MAF inspected and likely replaced. Mass air flow sensors are rarely repaired, as it is usually more cost-effective to replace them.
Because the MAF is instrumental in maintaining proper balance of air and fuel inside the engine, MAF failure can cause a range of engine performance problems. These may include low gas mileage, shuddering, stalling, knocking or pinging. Other common automobile problems can also cause these symptoms, so they don't specifically indicate MAF failure. These symptoms can appear, however, before the MAF fails to the extent that it will register the check-engine-soon light.
Sometimes the MAF will begin malfunctioning because it is dirty. Although the air that passes through the MAF is filtered, microscopic particles will still get through and accumulate on the sensor. Most of the time, this build-up won't be significant enough to affect the MAF, but severe build-up can cause interference. In these cases, you may be able to restore it to full functionality by removing and cleaning it.
The MAF is mounted to the vehicle's air cleaner box and connected to the computer with a wiring harness. If you remove the mounting bolts and wiring harness, you can remove the entire mass airflow sensor unit and open it to expose the sensor. The sensor is a small unit with two exposed wires; the wires heat up when the car is running, and the MAF measures the airflow by detecting how quickly the flow of air cools the temperature of the wires. Spraying these wires clean with MAF cleaner or electrical contact cleaner and leaving the MAF to air dry is the best approach to cleaning this sensitive instrument. Once it is dry, it can be reinstalled and the car can be started again. If engine performance is restored or the check-engine-soon light goes off, it is likely that the MAF was dirty and not broken.
- "Auto Repair For Dummies"; Deanna Sclar; 2008
- "Auto Upkeep: Basic Car Care, Maintenance and Repair"; Michael E. Gray and Linda E. Gray; 2007
- AutoShop101: MAF Overview