Poor Gas Mileage? Check These Air Intake System Parts

If your car has poor gas mileage and it’s not as fuel efficient, there could a part in your air intake system that needs servicing. This guide and video will show you 4 air intake system parts to inspect if your car is running out of gas faster.

4 Parts to Check If You Have Poor Gas Mileage

Mechanic reviewing air intake system parts that can cause poor gas mileage

The engine needs a certain amount of air to work efficiently. Air will pass through the engine air filter, MAF sensor, throttle body, and intake manifold before it reaches the engine, and these are the parts of the air intake system you’ll want to inspect if you have poor gas mileage.

Check these parts if your car is running out of gas faster

  1. Inspect the Engine Air Filter

    Remove the Air Filter Cover and the Air Filter

    All air has to be filtered before it enters the engine. Most engine air filter are easy to access and to find. They’ll be in the air box that’s connected to an air intake hose or snorkel. Air filter housings can be a little different. Some have clips you’ll need to lift up, and others might have screws or clamps. Once the clamps or screws are removed, lift the cover and remove the filter.

    Inspect the Air Filter for Damage, Debris, or Dirt

    Look at air filter see if it’s dirty. Check the fins and see if they’re separating, which could cause the engine to have difficulty drawing air. Cracks in the fins can also let unfiltered air into the engine.

    One way to test the engine air filter is to hold it up to a light. If you can’t see through it, it’s too dirty and needs a replacement.

    What Will Happen If I Drive with a Dirty Air Filter?

    If the engine air filter is dirty, it will have a hard time filtering air. You’ll need a clean air and the correct amount of volume, and a dirty air filter can damage other parts like the MAF sensor.

    More on how to inspect the air filter


  2. Inspect the Mass Air Flow (MAF) Sensor

    Remove and Inspect the MAF Sensor

    The MAF sensor meters the air volume and is usually attached near the engine air filter housing box. It’s an easy part to replace and requires disconnecting the electrical connector and removing any screws.

    If the engine air filter is dirty and not as capable at filtering air, dirt can collect on the MAF sensor and affect its ability to run. This will affect its calculations, cause poor fuel economy, and in most cases turn on a check engine light.

    Clean or Replace the MAF Sensor

    You can check the MAF sensor for dirt and clean it with MAF cleaner, but, generally, once it’s dirty and causing codes and a check engine light, it’ll need a replacement.

    What Will Happen If I Drive with a Dirty MAF Sensor?

    A check engine light can turn on if the MAF sensor is bad. The computer will receive incorrect readings, which can affect fuel economy and cause drivability issues.

    More on how to inspect and test the MAF sensor

  3. Inspect the Throttle Body

    Check the Throttle Body for Carbon Build Up

    The throttle body controls the air flow entering the engine. Typically, four bolts hold it to the intake manifold. It has a butterfly flap that opens and closes when the accelerator pedal is used. Some have an idle air control (IAC) valve, and some operate electronically.

    Carbon can build up on the backside of the flap and even on the body. This can cause issues with the throttle body and reduce air flow. The computer will need to compensate for the lack of performance and this can affect how well the engine runs.

    Remove and Clean the Throttle Body or Replace It

    Carburetor cleaner or brake parts cleaner can clean carbon build up on the throttle body. You’ll need to remove the throttle body to clean it, and a tooth brush is the best kind of brush to use.

    You don’t want to open the blade by hand, as that can throw off the calibration. The throttle body will be sensitive to being dropped, so we recommend handling it with care. If it’s dropped or the blade has been moved, you might have to reprogram the computer or replace the throttle body.

    After cleaning or replacing the throttle body, you also want to replace the gasket.

    Certain vehicles require an idle relearn update after removing the throttle body. The procedure may be different depending on the vehicle. You may be able to do this manually or with a scan tool, and generally you’ll run the engine for three minutes and then turn it off.

    What Will Happen If I Drive with a Dirty Throttle Body?

    If the throttle body is not performing a check engine light with a throttle body-related code will appear. Signs of a bad throttle body also include carbon build-up and weak or poor acceleration. You may notice a high or low engine idle that’s not running like it should be.

    Carbon build up might cause throttle body to stick. You won’t notice this as much with cable-activated types, but you may notice a delay when stepping on the accelerator pedal with electronically-controlled types.

    More on how to inspect and clean a throttle body

  4. Inspect the Intake Plenum

    Listen for a Whistle from the Plenum and Check It for Cracks

    The intake manifold or plenum is the last place air flow goes before entering engine. It needs to be sealed and mounted properly, and it does this with gaskets on backside.

    If it’s warped or cracked or the gaskets collapsed, unmetered air will enter the engine, and this will throw off the air fuel ratio, and cause a check engine light and drivability issues.

    Replace the Intake Plenum and/or Gaskets

    Replacing the intake plenum is fairly easy. You’ll be removing the throttle body and a couple bolts holding the plenum to the engine. You’ll lift it off, and it will probably have a bracket on the back, and then you’ll replace it with a new one or replace the gaskets.

    What Will Happen If I Drive with a Cracked Intake Plenum?

    If there is an air intake leak, the engine will be running rough and you’ll hear air whistling from that area. You could spray carburetor cleaner in those areas, but don’t spray it near the alternator or any flammable parts. If the engine performance changes and runs rougher or the idle changes, that’s where the leak is.

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Poor Gas Mileage? Check These Air Intake System Parts - 1A Auto
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Poor Gas Mileage? Check These Air Intake System Parts - 1A Auto
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If you have poor gas mileage, there could be a problem with the air intake system. Follow these steps from our experienced mechanics to diagnose and fix issues with this system yourself
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