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MAF Sensor — What is a MAF sensor?

What is a MAF sensor and how does it fail?

Mass Airflow Sensor — MAF

A mass airflow sensor (MAF) attempts to measure the density of the air coming into the engine. A mass airflow sensor sensor measures air density using either a hot wire or a hot plate and a separate incoming air

Mass Airflow Sensor

Mass Airflow Sensor

temperature sensor. The wire or sensor is first heated to a set temperature. Air flowing past the hot wire or plate cools it. The mass airflow sensor then applies more current to reheat the wire or plate to its set temperature. By tracking how much power it takes to keep the wire at the set temperature, along with the incoming air temperature reading, the PCM/ECM can determine the volume of air entering the engine and the air’s density (the number of air molecules in that volume of air). The PCM/ECM uses that data to compute the proper fuel to add to that volume of air.

What goes wrong with a MAF sensor?

The #1 cause of mass airflow sensor sensor failure is the accumulation of debris on the hot wire or hot plate. This can be caused by using an aftermarket oiled air filter or by neglecting to change a traditional air filter.

A bad or dirty maf sensor can cause a high idle

A mass airflow sensor detects the amount and density of air coming into the engine

In the case of an aftermarket “cold air intake” style filter, the filter media is often made of cotton saturated in oil. Oil soaked cotton fibers break off and attach to the hot wire or hot plate and then bake on due to the high heat. This debris forms an insulated coating that throws off the MAF sensor readings, causing the PCM/ECM to think the incoming air is warmer than it really is. In response, the PCM/
ECM commands a leaner fuel mixture, causing poor performance, engine misfire, a check engine light and even poor shifting (in an automatic transmission).

Signs of a failing MAF sensor

• Engine cranks but takes a long time to fire up, especially in cold weather or first start of the day.

• Engine stalls shortly after starting.

• You feel a hesitation as you accelerate, especially when the engine is under load.

• Rough idle

• Poor MPG

• Harsh transmission shifting

Can you clean a MAF sensor?

Sometimes. At least one company sells an aerosol spray MAF sensor cleaner. Read this post for the step-by-step instructions on how to clean a MAF sensor. Just about any DIYer can do this as long as you exercise care; the hit wire and temperature sensors are VERY delicate. Never scrub the wire or temperature sensor.

Replacement cost of a new MAF sensor?

MAF sensor cost varies based on year, make, model, and engine style, but range in price from $100 to $300. The MAF sensor is located between the air filter box and the throttle body in the intake manifold. To replace a MAF sensor, disconnect the electrical connector, loosen the hose clamps and swap in the new sensor, paying attention to the airflow directional arrows shown on the old sensor. Then tighten the clamps and reinstall the electrical connector.

©, 2018 Rick Muscoplat



Posted on by Rick Muscoplat

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