What They Are, How to Test and Replace (DIY)

Introduction

You take your car in for an oil change. The work is almost done when the technician comes out to talk to you. He’s holding your air filter and PCV valve and recommending that you replace both because they “look dirty.”

Without missing a beat, he explains how critical the air filter is to the efficient operation of your car. He tells you that a clogged air filter, or one that’s nearly clogged, can easily cost you 10 percent in gas mileage. With gas prices going through the roof, he adds, replacement will probably save you more than the cost of the filter. Plus, a dirty PCV valve, well, that’s never a good thing. Then he waits for your decision. It’s tough to make up your mind about an expensive air filter and PC-whatchamacallit valve when you don’t know what to look for with a PCV valve replacement.

It’s not difficult to check the air filter and PCV valve yourself. Here’s what you need to know.

What Is a PCV Valve?

The PCV (positive crankcase ventilation) valve is a one-way valve that recycles crankcase gases back into the engine to burn. A plugged PCV valve can result in a rough idle and poor mileage. Worse, it can cause costly oil leaks. Always follow your manufacturer’s replacement recommendations. N

Never replace a PCV valve simply because it ‘looks dirty.’ All used PCV valves look dirty. Below, we’ll show two ways to check the condition of your PCV valve.

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