7 Symptoms of a Dirty Air Filter in Your Vehicle

7 Symptoms of a Dirty Air Filter in Your Vehicle

Air filters ensure good airflow while guarding your intake manifold as well as your valve train from existing impurities in the air.



Generally, after a year of filtering out those impurities, they will clog and need to be changed, sometimes sooner, depending on other factors.


Without even opening the hood, you can determine if you have a dirty air filter. It’s a matter of watching and listening for certain symptoms that will present themselves. Here is a list of 7 symptoms of a dirty air filter in your vehicle:


Decrease in Mileage

This is the first noticeable thing that occurs with a dirty filter. When the airflow is blocked, your car will use more fuel to try and make up for the lack of oxygen. If you find that your fuel consumption is higher than usual, even in town, then you may want to check and/or replace your air filter. When you do, your fuel efficiency should improve and eventually go back to normal.


Engine Misses

air filter

Dirty filters impede airflow, causing your engine to run richer because it’s drawing more fuel to compensate for the oxygen it’s missing. This rich mixture can cause your spark plugs to be polluted, at which time they can misfire.


You will notice this condition in either starting problems or if you have a rough idle. This too can guzzle your gas, but replacing the filter will restore your firing situation to normal and get your fuel efficiency back.


Strange Sounds From the Engine

Next time you get in your car, start it up, let it warm up a bit, and then listen. Do you hear unusual vibrations or a “coughing” coming from the engine? Here again your filter is probably clogged. Depending on how long it has been clogged, you could have a spark plug that’s damaged from the rich mixture the engine has been sending it, due to the lack of air coming in.


Engine Light

Probably the most ignored indicator on a car’s dashboard, the engine light can actually tell you valuable things. Your engine has sensors all over the place, some of them monitoring your fuel and emissions. So a rich mixture and a lack of oxygen could definitely trigger the light. If it does come on, just give the filter a check. It won’t take long, and you could nip a problem in the bud.


Dirt Buildup on Outside of Filter

Your filter will start out as white in color, but will get darker as dirt, dust and other impurities build up on it. Some buildup can be tolerable for a while, but if it appears to be too dirty to you, then get it replaced. Better safe than sorry.


Reduction in Horsepower

The easiest way to explain this is to ask this question: How well does your vehicle accelerate? When you press the pedal, you should see a smooth, gradual increase. If it hesitates or coughs, then it is obviously lacking oxygen. Very likely, the smoking gun will be your air filter. Have it checked and replace if necessary.


Combustible Exhaust

This could be an indication of a more severe problem, but it starts at the air filter. If you have dark smoke or see flames emitting from your tailpipe, there is too much fuel in the system. As you’ve already learned, that indicates not enough air mixing with the fuel in a balanced way for proper firing. And where does that oxygen first enter the engine? That’s right, through the air filter.



Clearly, a clean air filter isn’t something you can take for granted. You could say that it’s a little thing that can make a big difference in your vehicle’s performance.

Learn to recognize these seven symptoms so you don’t allow too much time to pass before replacing your dirty air filter. Your car will thank you.


Bryce Newell is an automotive enthusiast who loves to write about the latest news, products, and DIY projects. While Bryce is an amateur in the field, he is passionate about cars and has been since he spent weekends in the garage helping his dad rebuild a 68 Dodge Charger as a kid.

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