5 Symptoms of a Bad Air Filter in Your Car

(Updated on December 15, 2022)

The air filter is a part of the vehicle that should be self-explanatory. As you probably know, the internal combustion engine can only operate if it has the proper amount of air and fuel. The air that goes into the engine is supplied by the outdoors. However, the engine requires this to be clean air without any dirt or debris.

That is where the air filter becomes important because it blocks all the harmful debris in the air from entering the engine. If you don’t have a functional air filter to block these harmful airborne contaminants, then it will spell trouble for the performance of your engine.

Top 5 Signs of a Dirty Air Filter

If you regularly get tune-ups and oil changes on your vehicle at a dealership, quick lube oil change place, or independent mechanic, then the shop employee may automatically check your air filter to see if it needs to be replaced.

Of course, you should not always rely on the employee to do this because they might skip this task just to finish their job faster. That is why you need to be aware of the symptoms of a bad or clogged air filter, so you will know when it is time to replace it.

Here are five things that often indicate you have a dirty air filter. If you suspect that’s the case, do a visual inspection of the filter or take it to an nearby automotive service center at the first available opportunity.

1) Poor Fuel Efficiency

bad gas in car symptoms

The functioning engine needs the correct balance of air and fuel to be mixed together for the ideal combustion process to take place. This helps maximize the fuel efficiency of your vehicle so that you get the most miles per gallon possible.

But if you have a bad air filter due to dirt and other particles clogging it, it will either block air from entering the internal combustion chamber or it will send dirty air into there. This will interfere with the combustion process and cause the engine to burn more fuel to compensate.

Related: 13 Important Tips For Better Gas Mileage

2) Bad Engine Performance

car makes rattling noise

The engine depends on an adequate supply of clean air for its combustion process to satisfy your acceleration demands. In other words, if you have a bad air filter, then don’t be surprised if you have trouble accelerating as you step on the gas pedal.

The engine will not respond well to dirty air in its chamber. This means it will have trouble generating enough power to accelerate the vehicle to the speed that you want, especially when under load.

3) Unusual Engine Sounds


There are different engine sounds that you will hear if you have a dirty or clogged air filter. These will be like coughing sounds which you do not normally hear.

These noises will occur the most when you step on the brake pedal and come to a stop. When the car is idling and then coughing sounds are heard, it means the engine is not getting enough good air inside of it.

4) Bad Spark Plugs

dirty spark plug

A dirty air filter can also cause the spark plugs to get dirty and not work as well as intended. This will limit the performance of the spark plugs when it comes to igniting the air and fuel mixture inside the internal combustion chamber.

Any problems with your engine performance will probably be connected to this. If a visual check confirms you have a dirty air filter, inspect your spark plugs to see if they are dirty too. If they are, then replace your spark plugs and air filter together.

5) Too Low or High Idling RPM

engine idle speed

When you turn on your engine and just leave it idling, the number of revolutions it makes should be in the 600 to 800 RPM range (but some older cars may idle slightly higher). This is considered the normal idling RPM range.

This is based on the proper amount of air and fuel being mixed together in the combustion chamber. Therefore, if you have a bad air filter which limits the amount of quality air in the chamber, then it will throw the RPM range out of order. If you notice the RPM falling under 600 RPM or over 1,000 RPM, then it’s a problem that must be addressed soon.

7 thoughts on “5 Symptoms of a Bad Air Filter in Your Car”

  1. hi my car is ford escort 1997 model ,the air filter was dirty I bought a new one but wen I put the pin that connects the air filter box to a engine the engine losses power and it turns it self off

    what do I suppose to do

  2. I noticed my car ML 320 Benz usually start very well with right sound but recently discovered to start will pose a difficult task as if there were no enough fuel. Thereafter, while fortunate to get car starting, after few hours when the car is stopped to start again might difficult. Please help

    • It could be a fueling issue as you’ve suggested, but it could also be an issue with one of the sensors. First, see if there are any check engine lights. Get those read, as they may give you a clue into what’s going on under the hood. If you’re having trouble with the diagnosis, I would bring it to a local mechanic you trust for more troubleshooting.

  3. Now a days per lts milage of my car is 5.5-6.0 where two months back it was 8-10 Km/Lt. I have changed four plugs within two weeks but not improve the condition.

    • There could be another issue, such as a fouled MAF sensor or bad O2 sensor. See if your car is throwing any codes and check for fuel leaks.

  4. I own a 1992 Lexus I can be driving and than all of a sudden my cars rpms go haywire snd my car sounds like it is reving so high my car continues to rev up but I have little power


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