How To Know When Your MAF Sensor Goes Bad, And How To Clean It

A mass air flow sensor is one of the numerous tiny widgets and gewgaws that make up a modern automobile's electronic fuel injection system. In the MAF's case, it tells the car's computer how much air is coming into the engine through the air intake, and thus how much fuel needs to be mixed into it to achieve the proper air/fuel mixture. While this sounds simple enough, the MAF also has to contend with changes in outside air temperature, air pressure, humidity, etc., all of which can change the amount of fuel needed for a proper mixture. It's a delicate, hard working little sensor and one that's incredibly important to the proper functioning of your vehicle.

Located between your air filter and your throttle body, the MAF is one of the more front-facing parts of your vehicle's fuel system. As such, it takes a fair amount of abuse from whatever dust or debris that gets past the air filter. Over time, enough dust and grime can collect on a MAF that it loses the ability to accurately measure the air coming into your engine. When that happens, the fuel system doesn't know how much fuel to mix into the air, so it just kinda wings it. This can lead to performance issues that run the gamut from "annoying" to "catastrophic."

It's relatively easy to tell when a MAF goes bad, especially in a newer vehicle. The first thing that usually happens is that your check engine light comes on. Your CEL is a message, and part of a system of messages, so pay attention to it! If, in concert with a CEL, you notice a distinct drop in your fuel economy or a rough and choppy idle, you may have a bad MAF sensor. Other annoying but relatively harmless symptoms include difficulty starting, stalling immediately after stalling, and stuttering or hiccupping as you drive along.

On the more dangerous end of the spectrum, a vehicle with a bad MAF sensor may stutter, surge, or hesitate under acceleration. Inconsistent or unreliable acceleration is incredibly unsafe, and could lead to a crash. A bad MAF sensor can also make an engine run lean, a condition where there isn't enough fuel in the fuel/air mixture that can lead to overheating, spark knock, or even permanent mechanical engine damage.

There are two ways to deal with a bad MAF sensor: clean it or replace it. Both of these jobs are pretty easy, but they require some mechanical know-how and a handful of basic tools. First, find your MAF sensor. It will be located somewhere between the airbox and the throttle body in the intake tube. Unplug the electrical connector from the sensor, then remove the bolt or screw holding it in place. Once you get the fastener off, the MAF sensor should just come right out with no problem. If it's stuck or it hangs up in any way, don't force it or you could damage it. Check all around the sensor to see if there's a secondary fastener like a clip or a release button. If not, gently rock the sensor back and forth to break it free and remove it.

Once the sensor is out, spray it down with MAF sensor cleaner (or an electronic contact cleaner if you can't get your hands on MAF cleaner), let it dry completely, and reinstall. If that cures your idling/running issues, congrats! You just saved yourself some money and time. If not, if your vehicle is still acting up after cleaning and reinstalling your MAF sensor, it's probably time for a new one. New MAF sensors are available from your local parts store and can run anywhere from $60 to $150 Yankee Dollars, or even more if you have something exotic. If you're not comfortable doing the work, or you simply don't have the time or inclination, any reliable mechanic (and even some good oil change places) can do the work for you.