When the air/fuel mixture is rich, a lot of the fuel going into the cylinder is unburnt. High fuel consumption is a direct product of a lean or rich air/fuel mixture which among other things is caused by a bad MAF sensor. Those can cause pretty much the same symptoms as a bad MAF sensor so there is no need to further diagnose the MAF before replacing whatever sensor is faulty. And P0104 means the MAF sensor circuit is intermittent which could indicate problems with the charging system or the battery, but that’s rare.ĭon’t be surprised if you get fault codes indicating problems with the coolant temperature sensor, O2 sensor, or fuel system. P0102 and P0103 mean MAF sensor circuit low input and high input respectively. P0101 indicates a problem with the voltage range. P0100 means MAF circuit malfunction in which case you should also check the wiring and the connector. In the case of a mass air flow sensor, you will get a fault code ranging from P0100 to P0104. That means the fault code will indicate precisely what the problem is, or what sensor is causing the problem. A check engine light will almost certainly tell you what’s wrong because misfires and lean or rich air/fuel mixture don’t trigger it. If you see a check engine light together with one or more of the symptoms we will mention, consider yourself lucky. And naturally, with all that black smoke puffing out of the exhaust, the car will definitely fail the emissions test. It can clog up the catalytic converter, the EGR valve, and even the exhaust manifold. This can be especially bad for the engine if you keep driving the car like this for a few hundred miles. That makes what’s called a rich air/fuel mixture which is the opposite of a lean air/fuel mixture. The ECU then throws a bunch of fuel into the engine and that excess fuel turns into smoke, soot, and carbon deposits. This is a sign that the mass air flow sensor is reporting that a lot more air going into the engine than it actually is. But if the mass air flow sensor is bad, thick black smoke will be present almost always, sometimes even at idle. It’s also worth mentioning that some black smoke is normal for diesel engines, especially during hard acceleration. Gasoline engines will almost never puff black smoke even in extreme cases. Black Smoke Coming Out of the Exhaustīlack smoke coming out of the exhaust is a common symptom of a rich air/fuel mixture in diesel engines. It can also happen during idling, and it can even happen while cruising which is especially unnerving. This usually happens when you shift gears and the engine speed first jumps before it starts decreasing. Once the mixture reaches the O2 sensor, the ECU readjusts it and the RPMs drop. The engine control unit then doesn’t send enough fuel into the combustion chamber to compensate, and the RPMs surge.

A faulty mass air flow sensor can report that a lot less air is going into the engine than it actually is. The same thing happens when the mass air flow sensor is bad. That’s a result of insufficient fuel delivery (too much oxygen), or in other words, a lean air/fuel mixture. If you have ever run out of fuel while driving, you will have noticed that just before the engine shuts down the revs on its own. In extreme cases where the mass air flow sensor is inaccurate, the delay can be as long as three to five seconds. Poor throttle response and hesitation are a result of that delay. That means the car won’t start accelerating until the air reaches the oxygen sensor. But when the mass air flow sensor is bad, it won’t notice or report the change in air volume. That helps the engine control unit further adjust the air/fuel ratio. Then, as the air and fuel are ignited, the O2 sensor registers how much oxygen is in the exhaust gas. Each time you press the gas pedal, the mass air flow sensor notices a change in air volume going into the engine and roughly adjusts the air/fuel ratio. Those are the mass air flow sensor and the oxygen sensor (O2 sensor). There are two sensors in all cars that primarily regulate the air/fuel ratio. 10 Symptoms of a Bad Mass Air Flow Sensor 1. And in some cases, the engine will often stall, and you will see a check engine light. Fault codes indicating misfires, and rich or lean air/fuel mixture are also common. Symptoms of a bad mass air flow sensor are hesitation, surging, poor fuel economy, poor performance, black smoke, and difficulty starting the engine. That’s why noticing the symptoms is very important. The problem is that the mass air flow sensor rarely triggers the check engine light or precise fault codes.

It directly impacts how the car drives, the fuel efficiency, performance, and exhaust emissions. The mass airflow sensor is one of the more important sensors when it comes to adjusting the air/fuel ratio.

Bad mass airflow sensor symptoms shift