8 Symptoms of a Dirty Air Filter
Is it time to change your car’s air filter? Due to its central function, your car’s air filter will inevitably get dirty over time. A clogged filter can reduce fuel economy, affect engine performance, and allow contaminants into your HVAC system.
We’ll explain the most common signs that indicate a dirty air filter needs replacing, how much it will cost to replace, and whether you can clean the filter instead.
Symptoms of a Clogged Air Filter
As mentioned above, a bad air filter can dramatically affect the performance of your car’s engine. So what are the signs of a clogged air filter? Here are 8 telltale symptoms of a dirty air filter:
1) Unusual Engine Noises
When your car is idling, you should hear the typical humming sound of a well-revved engine. If your engine’s air filter is clogged, the right amount of air can’t get into the combustion chamber, and you may hear crackling, sputtering, or coughing noises.
You may also hear a slight whistling sound if excess debris builds up on the filter screen, restricting airflow. Do not confuse this with a whooshing noise when accelerating. In this case, the engine will just suck in outside air through the filter.
In addition to the noise, your vehicle may also vibrate excessively due to a lack of air and an imbalance in the air-fuel ratio.
2) Lack of Performance
Because your engine isn’t getting enough air, it won’t run as efficiently as it should. A telltale sign of a dirty air filter is reduced acceleration.
If your car feels slow and a bit sluggish, the first thing you should do is check the condition of your air filter (always look for the cheapest and easiest cause when diagnosing car problems).
3) Check Engine Light Comes On
The maintenance light is another sign of a bad air filter. During combustion in the engine, your car naturally produces carbon deposits as a by-product.
When the air filter is clogged, it restricts airflow to the engine, resulting in insufficient airflow and over-burning of fuel. This causes excess carbon buildup and eventually the check engine light comes on.
The check engine light can mean hundreds of different things, so to be sure, you’ll need to scan your vehicle with a diagnostic tool.
4) Visually Dark and Dirty Air Filter
Clean air filters are usually white or off-white in color. For reusable K&N filters, they are closer to plum in color. As dirt and debris from the outside accumulate on the filter surface, the filter will gradually begin to darken in color. You can manually check the air filter to see if it needs to be replaced.
In many cases, it is enough to loosen a few clips on the air filter housing or cover and check. If you are still unsure if your filter needs replacing, remove it and observe it in daylight or with a flashlight to see how clogged it is. Note that the inner layer of the air filter’s paper may not have any visible residue or dust or debris even in bright light.
Always have a mechanic inspect your air filter every time you take your car in for service, and follow the manufacturer’s instructions for replacing your air filter. Your car dealer’s service department will usually check your filter for you automatically.
5) Reduce Fuel Consumption
Your car’s engine uses gasoline and air to start and generate power. When there is an insufficient air supply, your car’s engine will use excess fuel to make up for the deficiency (this is called “running rich”). This condition increases fuel consumption, so a drop in MPG is often a clear sign that your air filter needs replacing.
6) Engine misfires
A dirty filter reduces the airflow in your car’s engine, causing fuel to remain unburned. This fuel forms a soot residue that builds up on the tips of the spark plugs. As a result, the spark plugs will no longer be able to provide the proper spark to ignite the mixture, resulting in misfires and starting problems, causing the car to jerk when idling and especially when accelerating.
7) Black Smoke, Soot, or Flames from the Exhaust
As mentioned earlier, an insufficient air supply to the engine can cause incomplete combustion of fuel in the combustion chamber.
Unburned fuel leaves the engine through the exhaust, producing thick gray or black smoke. In rare cases, you may also see flames shooting out of the exhaust pipe.
8) Gasoline smell at start-up
A strong gasoline smell is another sign that your air filter is very dirty. Instead, this fuel will give off a distinctive gasoline smell, which is a reliable indicator of a bad air filter.
What does an engine air filter do?
The air filter prevents dirt, debris, pollutants and road insects from entering the engine and ensures proper airflow to the engine’s combustion chamber. If your air filter becomes too clogged and stops working, it can lead to poor performance and even engine damage.
To avoid this, automotive experts recommend replacing your filter every 12,000 miles or 12 months. But be sure to check your owner’s manual for the exact replacement interval for your vehicle’s air filter.
