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Do-It-Yourself Projects
Air Filter Fundamentals
By Mike Bumbeck /
Printable version
Degree of DifficultyEasy
Estimated Time120 minutes
120 minutes
Finding the Filter
The first step to changing the air filter is to find it. Open the owner's manual before opening the hood. Find the page that reveals locations of underhood service points and the illustration that shows where the air filter is. If there is no owner's manual, open the hood and look for either a football-sized box opposite the battery, or large circular unit or flat panel box atop the engine. Note locations and types of fasteners, clips, and hold-downs before removing anything.

If you have a digital camera, snap a "before" picture so that all turns out well afterwards. Make sure not to poke anything into the airflow sensor. Air filters are cheap. Replacement airflow sensors are not. Also take it easy on older, high mileage vehicles. Ham-fisted handling can damage intake hoses and tubes made brittle by years of exposure to underhood engine heat.
Back in the days of carbureted engines, the air filter was a big donut-looking unit that usually sat in a housing on top of the carburetor itself. Changing out the air filter involved removing the housing lid wingnut, the lid itself, and swapping out old for new.
Air Filters Back When Cars Had Carbureted Engines Were Big Donut-Looking Units
Automotive engineers were able to become more flexible with engine intake configurations as fuel systems moved away from carburetors and into fuel injection. Fuel injectors mix fuel and air into the engine right at the intake to the combustion chamber, eliminating the need to mix fuel and air in the intake manifold itself.
Today's Fuel Injectors Mix Fuel and Air into the Engine Right at the Intake
The airflow Sensor is crucial to the operation of a modern fuel injected vehicle, and must be kept clean. A clean air filter means a clean sensor. Be careful not to damage the airflow sensor or intake tubes when replacing the air filter.
Airflow Sensors Must Be Kept Clean; A Clean Air Filter Means a Clean Sensor
Here is an example of a flat panel air filter and air box. The air box and surrounding material also serves to dampen engine sound emanating from the intake. These baffles and materials can keep things quiet, but are sometimes a compromise between maximum flow and quiet operation.
Flat Panel Air Filter and Air Box
Performance air filters and cold air intake kits replace the factory setup and offer little in the way of sound and air restriction. This upgrade can deliver mild horsepower gains along with the growling sound of engine performance. The filters themselves can also be repeatedly cleaned and reused.
Performance Air Filter and Cold Air Intake Kit
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