What is a Throttle Body?

What is a Throttle Body?

Despite what you may have seen in sci-fi action movies, there are no explosions in space. The reason for this is simple: without oxygen, explosions just aren’t possible. Fire feeds on good old-fashioned air. Just as in snuffing out a candle, no air means no fire, no explosion, no combustion. In fact, the combustion in a car engine is in some ways controlled more by oxygen (or lack thereof) than it is by fuel.

The more air your engine gets, the more power it has to rev itself up. This is why aftermarket air intakes are such a popular item. If you can get a higher volume of air or lower temperature air into your engine, you can greatly increase your horsepower.

But what controls this airflow? The throttle body.

What is a throttle body?

The throttle body is a valve located along the piping between your air intake, and your intake manifold. It’s here where fresh air is slurped down into your engine for combustion – but only as much air as the throttle body will allow to pass. In the closed position, your throttle body keeps your engine almost entirely air-free, but when in the wide open position, this valve will really let that engine roar.

So how do you control your throttle body? It may be easier than you think.

You dictate the openings and closings of your throttle body’s butterfly valve every time you drive by using a conveniently installed foot pedal. That’s right – what we call the gas pedal might be more appropriately named the air pedal, since oxygen flow is what it’s more directly controlling.

Older carburetor-run vehicles would use a system of vacuums and pressure-sensitive triggers to release a complementary amount of fuel depending on your current airflow.
a modern engine with drive-by-wire throttle body

More modern vehicles use an electronic sensor to tell the onboard computer just how much fuel to dispense to match the incoming airflow.

In the old days, your gas pedal would be physically linked to your throttle body by a cable, but now sensors and servo motors are often opted for to get the job done.

Is your throttle body acting up?

When your throttle body isn’t working properly, some red flag symptoms would be an extra-high idle, or an extra-low idle. With a low idle, you might even notice your vehicle stalling out at red lights. Low idle speed typically is the result of throttle blade coking, restricting airflow, and essentially snuffing out the combustion inside your engine).

Unusually high, or inconsistent revs at an idle could be the result of too much air passing through the throttle body – likely the result of a vacuum leak. (New paragraph)

Either of these issues would drastically affect your engine performance, and most likely your Check Engine Light would turn on with a P2119 code, as well as, with the vacuum leak condition, P0171 & P0174 lean codes would also appear.

In modern vehicles, most issues with the throttle body will likely be electrical in nature. It’s important not to move the valve on your throttle body manually. Some car owners may do this in an attempt to clean the valve, but it may confuse your vehicle’s computer as to the resting position of your valve.

Check out all the fuel & emission system parts available on NAPA Online or trust one of our 16,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on the question of what is a throttle body, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Flickr.

about author

Jake McKenzie

Jake McKenzie is the Content Manager at Auto Accessories Garage, a quickly growing online retailer of automotive parts and accessories. Here he ranks, researches, and writes about everything from floor mats and seat covers to tonneau covers and performance parts. When Jake is not reading or writing about the automotive industry or attending the annual SEMA Show he likes to watch movies and perfect his homemade pizza recipe.

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