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Tending to MAF sensors

01/10/2014 @ 8:16am

Caring for the mass airflow sensor (MAF) on light-duty diesel pickup engines should be part of every preventive maintenance program. A traditional diesel engine employs a mechanical injection system. Newer pickup engines have electronic controls in place of an injection pump and nozzles.

For the system to determine load, some engines have a MAF sensor that measures the incoming flow of air. Airflow is an accurate indicator of the work the engine is doing. The information from the MAF sensor is used to help determine the quantity and timing of the injection events.

Though the MAF sensor is placed after the air filter, over time it gets exposed to dust and contaminants found in the air. These coat the delicate sensing element and cause it to skew.

Depending on the amount of contamination, the result may be an engine that seems to have lost its edge to a Service Engine Soon light being illuminated and a poor-running truck. Fortunately, restoring the MAF sensor to like-new performance is very simple. This procedure is applicable to both diesel and gasoline engines that employ a MAF sensor.

Follow these three steps as the SF Engine Answerman services a 2009 GMC Duramax MAF sensor.

  1. Depending on the application, the MAF sensor can be inserted into the intake duct or attached in series with ducting on both sides as a stand-alone unit on a pickup truck diesel engine. It is simple to locate, since it has multiple wires that attach with a plug. You can gain ready access to the MAF sensor so the electronic components can be seen. Be mindful of any gasket that may remain in place or is easily dropped or torn.

  2. Use a dedicated MAF sensor cleaner in an aerosol can. Never use carburetor or throttle body cleaners or generic electronic cleaners on this part due to the delicate nature of the MAF electronics. CRC MAF Cleaner is available in most auto parts stores for less than $8 a can. Do not touch any of the electronics with the spray tube. Generously bathe the sensing element with the cleaner. Numerous short, powerful blasts are usually the most effective.

  3. Often a MAF sensor will have other electronic parts such as a thermistor (the opposite of a resistor) that senses incoming air temperature. Use the cleaner on all visible electronic parts. You cannot hurt anything as long as only the spray touches it. Reinstall the MAF sensor and gasket, if applicable. Always tighten all of the intake ducting since any MAF system cannot compensate for air introduced after the sensor. This is identified as false air and will impact engine performance and idle quality.


About the Engine Answerman

Ray Bohacz has engine grease and field dirt under his fingernails from a life spent repairing vehicles and running a farm in New Jersey with his wife, Charlotte. His how-to articles also appear in Diesel Power, Engine Professional, Hemmings Motor News, and Speedway Illustrated magazines. Contact Bohacz via email at SFEngineman@earthlink.net.


Is overhauling an engine on your winter farm shop to-do list? Don't get started without consulting the Engine Answerman! Ray Bohacz has engine grease and field dirt under his fingernails from a life spent repairing vehicles and running a farm in New Jersey. His how-to articles also appear in Diesel Power, Engine Professional, Hemmings Motor News, and Speedway Illustrated magazines. Check out Ray's latest tips to start your overhaul off on the right foot!

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