Your vehicle's air intake system ensures that all air flowing into the engine for combustion is properly cleaned of dirt, properly measured, and properly controlled. Only then can it be precisely mixed with fuel in the exact ratio needed (14.7 parts air to 1 part fuel) for optimum combustion within the cylinders - a scenario where no fuel is wasted, and no power is lost.
In a modern engine equipped with fuel injection, there are three main components that perform these tasks - the air filter (cleaning), mass airflow (MAF) sensor (measuring), and throttle body assembly (control valve). Once air passes out of the air filter, it flows through the mass airflow sensor, then on to the throttle body. When either of these components malfunctions, engine running conditions become erratic - with uneven idle, hiccupping upon acceleration, and stalling being the most common symptoms.
Making a quick left turn in front of an oncoming bus is no time to realize your mass airflow sensor or throttle body assembly isn't cutting it. So in this guide, we'll explain how mass airflow sensors and throttle body assemblies work. We'll also examine how "replacement" (OE factory style) and "performance" (aftermarket) versions of these products differ, and how some can help create more power and/or fuel economy. Ultimately, you'll come out understanding when there's a need to replace a malfunctioning one, and why you may wish to indulge the want for an upgraded one with better performance.
What Is A Mass Airflow Sensor? ("MAF" Sensor)
Located between the air filter and intake manifold, the mass airflow sensor (also known as a "MAF sensor" or "air mass meter") measures the quantity of air that is flowing into the throttle body and intake manifold. It then reports this information to the vehicle's electronic control unit (ECU), which uses the data to calculate the amount of fuel that must be injected to the cylinders. To fine-tune the air/fuel mixture, the ECU also uses data from other sources such as the oxygen sensors in the exhaust system.
As such, a MAF sensor plays a crucial role in ensuring that optimum air/fuel levels are maintained for combustion. Should this sensor malfunction, the ECU can become confused by erratic readings and have a difficult time metering the correct amount of fuel.
It's critical to know the exact "mass" of the air going into the engine. "Mass" is different from "volume". Mass takes into account the density of air, which can vary greatly depending on altitude, temperature, barometric pressure, and a host of other climate factors.
Types of MAF Sensors
Automakers have consistently used various types of MAF sensors depending on their own engineering preferences.
"Hot wire" sensors are the most common type of MAF sensors. A hot wire sensor is equipped with a heated filament wire that's suspended directly in the path of airflow. When outside air is drawn past the filament, it cools down - causing its electrical resistance to drop. As the resistance varies, so does the current required to keep filament heated to a specific temperature. That current level is converted into voltage, then sent (as a digital measure of airflow) to the ECU.
A "vane air meter" sensor is another type of MAF sensor. It uses a spring-loaded mechanical flap that's gradually pushed open as airflow increases. As the flap opens, an arm rotates against a sealed potentiometer (also known as a rheostat or variable resistor), changing the electrical resistance and output reading to the ECU.
A "cold wire" sensor is a less common type of MAF sensor, named for the fact that it's not heated. Instead, small metal rods positioned in the airflow path are designed to resonate with higher frequency as airflow increases. This vibration frequency is then translated into a digital signal which defines total airflow.
Signs of a Malfunctioning MAF Sensor
No matter what type of design a MAF sensor uses, a malfunctioning one can cause the engine to hiccup and hesitate when throttle position changes. It may hesitate after starting, and idle speed may randomly fluctuate up and down even after it's warmed up.
An easy way to check for a faulty MAF sensor is to unplug it. If the engine suddenly runs better afterward, you'll want to replace the sensor. Or, use an OBD II diagnostic scanner to confirm the issue by reading fault codes on any vehicle sold in the U.S. since model year 1996.
Mass Air Flow Sensors - Replacement
If you're satisfied with your vehicle's stock performance, fuel economy, and general on-demand responsiveness, a Replacement mass airflow sensor will match or exceed the quality and durability of your OE one at a price that represents solid value.
To eliminate concerns that tend to plague lower-quality aftermarket parts, we take steps to ensure replacement MAF sensors we sell are sourced from manufacturers with proven track records of quality, durability and performance.
When it comes to replacement MAF sensors, we've got products available in different applicable forms for a wide range of vehicles spanning back decades. For example, there's the Beck Arnley Mass Airflow Sensor, Hitachi Mass Airflow Sensor, Bosch Mass Airflow Sensor (also includes select Ferrari, Porsche, Rolls, Bentley models), Spectra Premium Mass Airflow Sensor, and Genuine Air Mass Meter among others.
For more specialized applications, we've got the Denso Mass Airflow Sensor (Japanese makes 1999-2014), Mopar Mass Airflow Sensor (various Chrysler division makes), AC Delco GM Original Equipment MAF Sensor (mainstream GM vehicles from 1985-today as well as Saturn, Hummer, and GM-sourced Saabs and Isuzus), and the Motorcraft Mass Airflow Sensor (various Ford Motor Company brands including some Mazdas).
Mass Air Flow Sensors - Performance
It's important to note that OE mass airflow sensors are calibrated by vehicle manufacturers for precise measurement of airflow within a specific range. This ensures they work properly with pre-set flow rates of fuel injectors on a particular make and model. While OE MAF sensor calibration ranges may be flexible enough to handle the minor airflow increases of performance cold air intake assemblies, they aren't designed for major airflow increases that result from larger throttle bodies, intake manifolds, or performance cylinder heads.
And if you've got higher-flow fuel injectors, OE MAF sensors may not be able to handle their higher demands either. More specifically, original equipment MAF sensors cannot always provide the proper airflow signal to the ECU when other variables have been modified.
For MAF sensors within a housing, the inside diameter of that housing may physically be too small to handle increased volumes of air flowing through. In other words, OE sensors can actually create a bottleneck.
Performance mass airflow sensors address these issues because they are purpose-built to measure much higher levels of airflow, with larger diameter housings to ensure airflow is smooth all the way from the filter to the combustion chambers. Naturally, they will produce greater gains from performance cold air intakes. But we can't emphasize enough that performance MAF sensors are essential for highly modified fuel-injected engines.
When it comes to specific MAF sensors that deliver on these promises, we carry these performance-oriented ones available for a wide range of vehicles spanning back decades: The Bremi Mass Airflow Sensor, Granatelli Motor Sports Mass Airflow Sensor, and JET Mass Airflow Sensor.
For more specific applications, we've also got the PMAS Draw-Thru Mass Air Flow Sensor Kit and the BBK aluminum Mass Air Meter for Ford Mustangs. Ford owners with 2001-03 F-150 SVT Lightning trucks should check out the Ford Performance Mass Air Meter. For V8-powered GM models from 1997 through today, there's the PSI Mass Airflow Sensor. Edelbrock's Mass Airflow Sensor Kit is designed for GM and Ford V8s used in racing applications (from 1940s engines converted to fuel injection through today).
In addition to performance MAF sensors, we also offer sensor mounts and adapter kits. If you're building a custom intake or swapping a modern engine into an older vehicle, such mounts enable sensor attachment - and the adapter kits are an easy way to mate a high-flow air filter to a new MAF sensor.
What Is A Throttle Body?
Located behind your engine's air filter housing and mass airflow sensor, a throttle body regulates how much air enters a fuel-injected engine. Inside the throttle body housing, a butterfly valve (hinged metal plate) determines the airflow rate by rotating open so that more air can pass through when the accelerator pedal is depressed.
As that air passes through a round, tube-shaped section of the housing, information is gathered from various sensors and relayed to the ECU. This data, along with other information, is used to calculate an ideal fuel mixture for the amount of air flowing in.
Types of Throttle Body Assemblies
Throttle body assemblies are known as either "mechanical" or "electronically controlled." On a mechanical throttle body, the butterfly valve is operated by a spring-loaded arm piece that's directly linked to a vehicle's accelerator pedal by way of a manual cable. Newer vehicles that do not have cable linkages to the accelerator pedal will use throttle body assemblies with computer-controlled servo motors to move the butterfly valve as needed. These servo motor assemblies are described as electronic throttle controls.
On either setup, a knob on the outside of the housing rotates as the butterfly valve moves in order to give feedback to an attached throttle position sensor. This sensor then sends an electronic signal to the ECU so that fuel flow is adjusted to match the amount of air that's now entering the engine.
On the outside of the throttle body assembly will be a hole for mounting a manifold absolute pressure (MAP) sensor. This port connects to a small air duct that runs into the pressure chamber behind the throttle plate. As more air flows in, the MAP sensor will read a higher pressure, which the ECU uses to verify calculations for fuel flow rate.
Another port will exist for mounting an Idle Air Control (IAC) valve, which controls the amount of air the engine gets at idle. On cold starts, this valve allows more air to pass through so that the engine warms up faster when idling.
For regulating overall idle speed at all times (not just during warmup), mechanical throttle bodies will have an idle speed adjuster screw that can be tightened or loosened in its mounting port. As it's loosened, the screw retracts out of the way inside a dedicated air duct so that more air can pass through at all times.
For the purposes of quick winter warm-up, some throttle body housings may be equipped with small nipples that can be connected to the vehicle's coolant lines. These allow just enough warm coolant to pass through so that any moisture that's frozen will quickly thaw away. In order to prevent air inside the throttle body from becoming too heated, the amount of coolant flowing through is kept to a minimum.
Throttle body assemblies for newer vehicles will most likely be equipped with an additional nipple that attaches to a emissions system vacuum line. This nipple will have its own small duct that runs into the throttle body chamber.
Signs of A Malfunctioning Throttle Body
Typical throttle body issues are electronic, such as wiring circuits with too much electrical resistance due to corrosion, or an "open" condition where wiring is broken, loose, or not grounded properly. Sensors mounted on the throttle body housing may be failing, causing the vehicle's ECU to become confused. Servo motors that adjust the butterfly valve on throttle bodies with electronic controls wear out also.
A malfunctioning throttle body can cause an engine to stumble and hesitate noticeably upon acceleration. Sometimes, throttle response to the accelerator pedal may be consistently delayed. The engine may stall completely after startup, under load, or at idle. In worst-case scenarios, you may lose practically all of your throttle control and the vehicle won't accelerate.
On newer vehicles with more electronics, cycling the ignition key off for a few seconds before cranking the engine again will sometimes make faulty conditions go away.
The metal housing of a throttle body usually isn't the problem - however, carbon deposits and dirt do build up over time and diminish smooth operation of the butterfly valve. If gunk accumulation is the only issue, a simple removal and cleaning of the throttle body should correct the issues. Throttle bore wear can happen after many miles, and this typically requires replacement of the entire unit.
Throttle Bodies - Replacement
A replacement throttle body will restore the reliability and responsiveness of a factory original equipment unit. In fact, odds are good that the manufacturers of Replacement throttle bodies we offer were contracted by your automaker to build the ones installed on their own assembly lines.
If you've got a German car from today back to the 1990s, take a look at the Bosch Throttle Body Assembly and Standard TechSmart Fuel Injection Throttle Body Assembly. Bosch units feature electronic adjustment motors, while the Standard brand units offer mechanical setups when applicable on older vehicles. Note that all of these units also offer a selection for American and Asian vehicles from the 1990s through today.
Hitachi Fuel Injection Throttle Body units specialize in Nissan and Infiniti models back to 2002 as well as General Motors brand vehicles including Saturn and Hummer. Additionally, Dorman Throttle Body Assemblies feature additional GM-powered vehicles sold by Isuzu and Saab as well as other American and Asian makes. AC Delco GM OE Fuel Injection Throttle Body units are for General Motors models only from 1996 through today, with both mechanical and electronic setups. Spectra Premium Fuel Injection Throttle Body units offer all-electronic setups for select American, German, and Japanese cars from the mid-1990s through today.
For the more advanced mechanic, we've also got a selection of smaller individual components that are part of throttle body unit assemblies such as electronic control modules, actuators, motors, throttle position sensors, relays, mounts, bushing pieces, and more! Just use the check boxes along the left side of the screen to narrow your search.
Throttle Bodies - Performance
A performance throttle body assembly is a great way to help your engine create more power - especially if you've added a supercharger or turbocharger. But whatever your modifications are, the greater airflow ability of a performance throttle body will really give your engine a shot in the arm. Why? A more powerful engine needs a greater volume of air, and a larger throttle body will help deliver exactly that. After all, it doesn't make sense to install a performance air intake setup if the airflow is only going to get choked further on down the line.
Other modifications that can see additional gains from performance throttle bodies are exhaust headers, performance air intakes, custom exhaust systems, and electronic tuners that remap spark timing and fuel delivery.
An engine is really nothing more than a big air pump. Everything else being equal, the more air we can pump through it, the more power it will make. Performance throttle bodies are built with airflow tubes that are larger in diameter than OEM ones. Naturally, this increases airflow. Throttle bodies are given an airflow rating based on the number of cubic feet of air that can pass through in one minute ("CFM" for short). Use this rating as a gauge when making your selection.
With Careful Choices Comes More Power
Packing more air into your engine allows more fuel to be burned, which creates more power. Because aforementioned sensors measure the airflow rate, the car's engine control computer can take note of this increase and up the amount of fuel delivered to the pre-combustion chamber. Peak air-to-fuel ratio that produces the most complete combustion is maintained, and so will your power gains.
As we mentioned earlier, power gains will be lost if the air-to-fuel ratio should deviate from the optimum mix - in either direction. For example, pumping more fuel into an engine without a corresponding increase in air would not produce more power - only unburned fuel going out the exhaust pipes. Likewise, adding air without increasing fuel will cause a "lean" running condition and a noticeable drop in power.
We recommend choosing the largest throttle body sizes only if you've made fuel delivery and high-power modifications to your vehicle. Otherwise, you'll be adding more air than the fuel system can keep up with. Power gains will be disappointing. If your vehicle is stock or "mildly" modified with a cold air intake or a cat-back exhaust, for example, go with a slightly larger increase over OEM size.
Improved Throttle Response
When you consider that a throttle body is just a valve, it's easy to understand how a performance throttle body yields quicker throttle response. Most auto manufacturers measure airflow at peak rpm's, then choose a throttle body diameter to ensure that 50% throttle will produce exactly 50% airflow. This results in a more gradual response that drivers who are NOT interested in performance would value, because they equate it with smooth drivability.
Because the butterfly valve on a typical performance throttle body is designed to open proportionately wider at low rpm's, power is created with less delay. When you combine that steeper response rate with additional torque produced by the engine, you get a sharper bite that's noticeable at low rpm's.
Performance Throttle Bodies We Offer
We've got a large selection of performance throttle bodies, most of which are crafted from lightweight aluminum. To name just a few for more recent vehicles, the Holley Billet LS Throttle Body covers a number of 1997-on Chevy cars and trucks equipped with LS-series V8 engines. We've also got the BBK Power-Plus Series Throttle Body (wide selection of makes & models) and Jet Powr-Flo Throttle Body (2003-15 GM & Ford) throttle bodies.
If you're looking to upgrade an older vehicle already equipped with fuel injection, we've got the Skunk2 Alpha Series Throttle Body (best value), Pro Series (higher performance) and the Blox Racing aluminum Billet Throttle Body for Honda and Acura engines from the 1980s through today.
The Holley Hi-Flow EFI Throttle Body covers assorted Dodge, Ford, and GM V8s from 1986-on, while their Two Barrel Performance TBI is for GM pickups from 1986-95, and the BBK Power-Plus Series Throttle Body covers Chevy and Ford back to 1985.
If you'll be upgrading your classic from a carbureted setup to fuel injection, you're going to need a throttle body assembly to replace that carb. Fortunately, we've got throttle bodies from Edelbrock and Holley designed with just this adaptive ability to mount on square bore intake manifolds where a carburetor once sat. For those who wish to maintain the original look of a carburetor, the Holley Terminator Stealth EFI Base Kit is just one of a few we offer that looks like a carb from the outside!
2018 Jeep Wrangler JK
After purchasing one of the last JK-body Wranglers in 2018, Eric immediately began enjoying the surprisingly spirited performance that the V6 engine and 6-speed manual transmission provided. This was addicting. After customizing the Jeep with 2 inches of lift, more stylish rims, and bigger off-road tires, Eric really liked the way it looked. However, he found the extra weight and larger diameter of the fatter tires dulled his off-the-line performance - just a bit, but enough to be noticeable.
I order to dial up the power slightly without spending a lot of money or making major modifications, Eric chose to install a cold air intake/filter setup and the BBK Power Plus Series Throttle Body. With aluminum construction, he knew it would be lightweight and free of corrosion for the life of his vehicle. And thanks to its larger-than-stock diameter, his new performance throttle body gave him enough of a power boost to restore factory performance levels. After seeing no issues with his factory MAF sensor, Eric chose to leave it in place.
2015 Ford Mustang
After becoming the owner of a 3-year-old 2015 Ford Mustang Boss Edition 5.0-liter, Sal finally felt he owned a car that was equally as invigorating to drive as it was to look at. But, as often happens to enthusiasts of powerful performance vehicles, impressive levels of power soon lead to a wish for even more power. This was especially true for Sal, who envied how the bigger engine in that year's Mustang GT350 version broke the 100-horsepower-per-liter mark with 526 horsepower from 5.2 liters.
To up the power output of the standard V8 his Mustang had, Sal got to work. After installing a complete performance exhaust system, he knew his engine was well on the way to breathing better. But to add to that, Sal installed two more performance items to get the most out of that new exhaust.
To allow a larger amount of air to reach the engine without bottlenecking, Sal opted for the Grams performance Drive-By-Wire Throttle Body because of its larger bore size, more powerful flap actuator motor, lightweight aluminum housing, and upgraded sensor(s). He also chose to add the Edelbrock Mass Air Flow Sensor Kit because of its ability to properly measure high-velocity airflow streams that his engine now enjoyed thanks to the other upgrades.
To sum things up, if you're happy with the lifespan and performance of your vehicle's mass airflow sensor and throttle body assembly, you won't go wrong with our replacement OE-style units - many of which provide improvements over factory parts you'd pay more for at a dealership.
If you're making smaller levels of power increases to your engine, you'll definitely benefit from a performance throttle body assembly which allows more air to pass through it without bottlenecking. If you're boosting your engine in big ways that will require significantly larger amounts of air drawn into it (adding a turbo- or supercharger, for example), then you will want to add a performance MAF sensor as well. Doing this will ensure that the greater amount of air being drawn in will not exceed the measuring capabilities of an OE unit.
We understand you may have questions about what you see on our website. We're happy to help make your shopping experience easier, so we've got knowledgeable product reps on call seven days a week that will be glad to listen and share any expert advice possible - without high-pressure sales tactics. We look forward to hearing from you!