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Old August 26th, 2011, 05:00 PM
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Exclamation How To Diagnose a bad Mass Airflow Sensor

Mass Airflow Sensor Failure Symptoms

Do Not Touch The Wires With Your Fingers or let the Wires touch Anything

Diagnose a bad mass airflow sensor to avoid further car problems. 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 analyzed to see if the light is related to the mass airflow sensor.

Computer Analysis
An auto mechanic can analyze 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.

Particle Buildup
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 buildup won't be significant enough to affect the MAF, but severe buildup can cause interference. In these cases, you may be able to restore it to full functionality by removing and cleaning it.

Do Not Touch The Wires with your FINGERS
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.

Remove the MAF sensor from your engine. While the specific location of the MAF varies by engine, the MAF is typically located between the throttle body and the air filter on your car. It will be a sensor with an electrical plug connected to it. Remove the sensor by unplugging the MAF electrical sensor, then using the appropriate tool, typically a torx wrench or a small phillips screwdriver. Take extreme care not to physically touch the sensor with your hands as you will leave oil deposits on the sensor.

Use a MAF safe electronic cleaner to liberally spray the sensor. Do not use carburetor or brake cleaner. You can purchase MAF safe electronic cleaner such as CRC Mass Airflow Sensor Cleaner at large automotive supply stores. Following the cleaner directions, spray the sensor and allow it to dry, repeating the process.It is important to know that the wire is very fragile and can be damaged easily. Hold the aerosol can far away, at least two feet from the sensor when spraying on the wire. Any force on the wire and it will break. Allow a mist to rain down on the wire and surrounding area. Allow to air dry before reinstalling.

Reinstall the cleaned MAF sensor into the intake tract, and then drive the car to see if the vehicle operation has improved. If there is no improvement in the vehicle's performance, the MAF sensor may have failed, the electrical connector may be damaged, or there may be a tear or leak in the intact tract, which is allowing additional air past the MAF sensor

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Last edited by JSoko; August 26th, 2011 at 05:17 PM.

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