|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.
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.
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
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.
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.