Automotive Master Technician

Every sensor on or in a computer-controlled car or truck talks to the “on-board PC” in a kind of language you’ve never heard or seen. All of the inputs are in a voltage-speak and are all numbers. All of these signals to and from the PC travel in and out at up to 300 times per second. That is some party line!

Your PC knows the amount of air going into or being inhaled by the engine. It knows the temperature of the air, the barometric pressure, the outside temperature, if it’s raining and if the engine is pinging. It knows if the engine has too much fuel or too little fuel being delivered to it. It knows the temperature of the coolant and the catalytic converter, and it knows how cold it is inside the car and how that compares to the temperature you are requesting.

Most of the voltages start at zero and have a high end of 5, 8 or 12 volts. For instance, 1.0v means low and 5.0v means high. Or 1.0 means cold and 5.0 means hot, hot, hot.

But most scanners convert these numbers to a range we can understand, like 20 grams or 212F or 45% throttle.

The mass air flow sensor (MAF) tells the PC how much air is flowing into the engine; we read that data in grams. So a little air means no foot on the throttle and lots of air means foot to the floor. Think of the mass air flow sensor as a goal post with a filament across the top arms. It actually looks like the filament inside a clear light bulb.

The PC sends voltage to the filament and then monitors the electricity needed to keep it warm or hot. The MAF starts lying when this filament gets covered with trash, bugs and dirt. Pretend you are in a tunnel and naked. You could easily tell how much air is flowing thru this tunnel and what the temperature is. How good of a job could you do if I covered you with 5 layers of clothing, gloves, hats and full face coverings? That is exactly what happens to your MAF: it gets covered up and starts lying about its environment.

We want to see about 5-10 grams depending on the size of the engine. This gram number determines fuel trim. A dirty MAF won’t see all the air, so it tells the PC to trim the fuel down. 1 gram at idle is a problem.

So if you want to save yourself from $45 to over $100, go to the auto parts store. Ask them to point out where the MAF is located on your car, and ask them to show you what it looks like. You may need special tools. Then buy some CRC Mass Air Flow Sensor Cleaner. The CRC product was developed specifically for cleaning this very delicate sensor.

Pull the negative battery cable. Remove the MAF sensor. DO NOT touch the filament. DO NOT get your wife’s toothbrush out and scrub it. If you damage it, you just cost yourself hundreds of dollars. Just spray it off like you would spray a small painted wire with carburetor cleaner when you only want to remove the paint. Do it maybe 3-4 times and once every 30-40,000 miles.

Let it dry, reinstall, connect the battery and drive away. It will take the PC just a few hours to reset those parameters that just changed because the MAF is now cleaner and working more precisely.