Auto Repair: Check the Air Filter

man checking under car hood

Because gasoline engines run on a mixture of air and fuel, the air has to be cleaned before it's mixed with the fuel. The air filter removes dirt and dust particles before they can enter the combustion chamber. In the "olden days," most air filters were inside large, round air cleaners that sat on top of the carburetor. Today's fuel-injected engines have a rectangular air filter inside a cold aircollector box located near the front of the engine compartment; see Figure 2-2.

Auto Repair for Dummies Figure 2-2

To find the rectangular cold air collector box in your vehicle, pop the hood and follow the large air intake duct away from your engine. If you have an older vehicle with a large round air cleaner, you can't miss it. If you don't know how to get the hood of your vehicle open, see your owner's manual.

To keep your engine functioning efficiently, be sure to check your air filter regularly as part of the under-the-hood check, and replace it at least once a year or every 20,000 miles, whichever comes first. (Replace the air filter more often if you regularly drive in a dusty or sandy area.)

In most newer, fuel-injected vehicles, the air filter is found inside a rectangular box called a cold air collector box (see Figure 2-2). It's usually close to the front of the vehicle near the inside of one of the fenders. Air that's scooped up by the front of the vehicle moves through an air intake tube into the air filter inside the box (see Figure 2-2). On older fuel-injected engines and carbureted engines, the filter is found in the air cleaner, which sits atop the engine. As you can see in Figure 2-3, it's large and round with a snorkel sticking out of the side to facilitate the intake of fresh air. Your owner's manual should have instructions on how to locate and get at your air filter.

Auto Repair for Dummies Figure 2-3

To find out if your air filter needs to be replaced, just lift it out (it isn't fastened down) and hold it up to the sun or to a strong light. Can you see the light streaming through it? If not, try dropping it lightly, bottom-side down, on a hard surface to jar some dirt loose. (Don't blow through the filter — you can foul it up that way.) If you drop the filter a few times and it's still too dirty to see through, you need a new one.

Because the air filter extracts dirt and dust particles from the air, you should change it at least once a year or every 20,000 miles, whichever comes first — unless yours gets very dirty before then. If you do most of your driving in a dusty or sandy area, you may need to replace your air filter more often.

From Auto Repair for Dummies, copyright © 2009 by Wiley Publishing, Inc., Indianapolis, Indiana. Used by arrangement with John Wiley & Sons, Inc.

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