Bad Engine Air Filter Symptoms and Replacement Tips

Reviewed by

Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Written by CarParts.com Research Team - Updated on February 10th, 2025

Reading Time: 5 minutes
Summary
  • Your vehicle’s engine air filter is part of its induction system. It cleans the air entering your engine before the start of the combustion process.
  • Inoperative engine air filter symptoms include visible dirt or debris, odd engine noises, and black exhaust smoke.
  • It doesn’t take too long for a DIY pro to finish an engine air filter replacement, but beginners might have a tougher time. Bring your vehicle to an auto repair shop if you aren’t confident in your abilities.

If you’re noticing dirty air filter symptoms on your daily drives, it’s probably time to switch out your engine air filter for a new one. The air filter helps the engine run well and keeps the air in its different sections clean.

In this article, we’ll be taking a look at what engine air filters actually do, the signs that they’re faulty, and some tips for how to replace them.

The Importance of Engine Air Filters

Your vehicle’s engine air filter is part of its induction system, which also includes the cylinder heads and the intake valves. It cleans the air entering your engine before the start of the combustion process.

Clean air makes for cleaner ignition, meaning fewer particulates in the exhaust. About 10,400 gallons of air flow through a vehicle’s engine air filter for every gallon of fuel injected through the system.

Inoperative Engine Air Filter Symptoms

If you suspect you need to change your vehicle’s engine air filter, watch out for the following symptoms:

Visible Dirt or Debris

When you change your vehicle’s engine oil, you can take a look at its air filter. See if there’s dirt trapped between the filter pleats or a thick layer of dirt on the material.

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Drop the filter on a concrete floor and see what shakes out of it. If you see dirt on the floor after you drop it, replace the filter.

If you see that the seal around the edges of the filter is compromised, or if you notice when you remove the air filter cover that it isn’t holding its shape (sagging and out of place) replace it with a good air filter. You’ll pay more, but there’s a lot at stake. If your air filter housing is cracked, don’t try to fix it with tape. Replace it. it’s worth the cost to save your engine. | Image Source: Richard McCuistian

If the debris is minimal, you can use a can of compressed air to loosen the dirt and keep using the filter. However, if you shine a light through the filter and it isn’t visible through the filter’s pleated material, the filter is unsalvageable. Note though that even if you can see light through the filter (make sure there are no holes torn in it) and it gives up dirt when you drop it, replace it.

Before we go into the symptoms listed that indicate a near or totally clogged air filter, let’s pause here to say that engines don’t usually give noticeable symptoms unless the air filter is in horrible shape.

If you splashed through some really muddy water and some of it made its way into the air intake of the filter, it may clog the filter very rapidly with mud.

Even if the filter is just wet, it’ll seem to be clogged until it dries out. If the symptoms described here come about suddenly, you either ran through some water or a critter has built a nest in the air intake or the filter housing.

If these symptoms come about slowly over time due to poor maintenance while driving in extremely dusty conditions, the air filter is the first place to look.

If you splashed through some really muddy water and some of it made its way into the air intake of the filter, it may clog the filter very rapidly with mud.

Richard McCuistian, ASE Certified Master Automobile Technician

Odd Engine Noises

If your vehicle’s engine starts sputtering, coughing, or making popping noises, it’s possible that it’s starved for clean air. Odd engine noises are some of the dirty air filter symptoms you need to keep an ear out for.

A dirty air filter limits the air supply flow going into the engine, which in turn affects the air-fuel mixture in the cylinders. This leads to the engine running inefficiently and making strange noises. If there isn’t enough air in the engine’s cylinders, it can’t thoroughly burn up the injected fuel.

Black Exhaust Smoke

When the air-fuel mixture in the cylinders has too much fuel, the resulting exhaust gas ends up carrying the unburned fuel through the exhaust system. Black smoke coming out of the exhaust system is a clear sign of this.

Unburned Fuel Smell

Along with black smoke, the excess fuel in the exhaust gases will give off a bad, unburned fuel smell from the exhaust. This clogged air filter symptom will show up when the air filter is blocked.

Other Symptoms

Some other symptoms related to a clogged engine air filter include increased fuel consumption, an illuminated check engine light, and poor engine performance. Increased fuel consumption and poor engine performance are the result of the air-fuel mixture imbalance caused by a clogged air filter.

Engine Air Filter Replacement Tips

If you’re looking to replace your engine’s air filter, it can be a bit tricky.

First, you’ll need to locate the air filter housing underneath the hood. On older vehicles, you’ll find it on top of the engine. Modern vehicles have it sitting opposite the engine and mounted to one of the fender wells at the end of a large intake hose.

Next, you’ll need to remove the screws or clamps holding the housing together. Note that removing the old, dirty air filter isn’t enough. Wipe down the housing with a clean rag. and keep any debris from falling into the intake and the carburetor if your vehicle has one. Also, remove the breather filter.

Install the new air filter and breather filters, and reattach everything you disassembled. You might also want to replace the PCV filter.

It doesn’t take too long for a DIY pro to finish this job, but beginners might have a tougher time. Always bring your vehicle to an auto repair shop if you aren’t confident in your abilities or are unfamiliar with auto maintenance tasks.

How Often Should You Replace the Engine Air Filter?

You might be wondering how often you need to replace an engine air filter. In general, a new engine air filter will be good for 15,000 miles. However, if you drive in a dusty or high-pollution area, you might need to replace it sooner. Consult your vehicle’s maintenance manual for more specific instructions.

And there you have it. Those are the common dirty engine air filter symptoms you need to keep an eye out for. Replace your filter as needed, and always consult a professional mechanic if you aren’t completely sure what you’re doing.

Where to Get New Engine Filters for Your Car

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