How to Clean a MAF Sensor on a BMW


A BMW’s mass air flow (MAF) sensor is located on the intake side of the motor. The MAF is responsible for telling the engine’s electronics how much air is entering the intake of the engine to ensure that the motor runs correctly. If the MAF becomes dirty or contaminated, the signal may not be correct, resulting in a rough idle and even the dreaded CEL (Check Engine Light), which can cause a BMW to fail an emissions test. Cleaning the MAF is a straight forward process with the right approach and tools.

Things You'll Need

  • Socket set and ratchet
  • Flat-head screwdriver
  • Mass air flow sensor cleaner
  • Microfiber towel
  • Open the hood on the car. Locate the airbox. This will vary depending on the model of BMW but will be located somewhere near the intake side of the engine. Disconnect the wiring harness from the MAF by pulling the retaining clip up.

  • Remove the bolts that hold the airbox in place in the engine bay. Loosen the hose clamp that holds the intake to the airbox. Remove the hoses that go to the intake and the exhaust side of the airbox and remove the airbox from the engine bay. You may need to do some maneuvering and jiggling to get the airbox out.

  • Set the airbox on a workbench or somewhere clean. Remove the MAF from the airbox by prying the retaining clips out of the way.

  • Spray the MAF cleaner onto the entire screen of the MAF, being careful that you don’t touch any parts with the plastic nozzle on the can of the cleaner. Wipe the MAF housing, intake tube and nearby areas with a clean microfiber towel.

  • Reinstall the MAF in the airbox. Carefully reinstall the airbox in the engine bay with the bolts that hold it in place. Reconnect the intake and exhaust tubing and tighten any hose clamps. Start the motor to ensure that it is running correctly.

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