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It's rare for a vehicle to come equipped with an air fuel ratio gauge from the factory. Aftermarket options are widely available. Many enthusiasts use these gauges to keep an eye on modified and factory turbocharged engines.

Install Level of Difficulty


What are Air Fuel Ratio Gauges?

There are two types of air fuel gauges: wide band and narrow band. Wide band gauges give you a 'snapshot' of what's going on inside your vehicle’s combustion chamber. Narrow band air fuel gauges are more vague as they receive their signal from your vehicle’s factory oxygen sensor.

How do Air Fuel Ratio Gauges Work?

To produce optimum power output, your vehicle’s engine needs an air fuel ratio of approximately 14.7:1. This is called the stoichiometric ratio, or 'stoich' for short.

If your engine runs too lean, you run the risk of scattering its internal parts all over the road, drag strip, or race track. If your engine runs too rich, it won't generate as much power as it could if the air fuel ratio were dialed in properly. Your gas mileage may suffer, as well. The air to fuel ratio gauge helps enthusiasts keep an eye on modified engines.

How are Air Fuel Ratio Gauges Made?

Gauge faces are often screen printed. Though machines are used to manufacture many of the gauge's parts, the finished product is often assembled by hand.

Why do Air Fuel Ratio Gauges Fail?

  • The gauges themselves rarely fail; however, your oxygen sensor may need to be replaced to ensure accurate gauge readout.
  • Oxygen sensors fail when excessive carbon deposits build up on them.

What are the Symptoms of Air Fuel Ratio Gauge Failure?

  • Gauge readout is inconsistent with the way the engine runs. For example, you may know for a fact that your engine runs well, but the gauge reads way out of range in either direction.
  • Gauge needle fails to move or pins itself against the far clockwise side of the gauge.

What are the Consequences of Air Fuel Ratio Gauge Failure?

  • Engine damage may result if your gauge fails to alert you to a lean condition.
  • A malfunctioning oxygen sensor may throw a check engine light that comes on and stays on.
  • A malfunctioning oxygen sensor may also effect fuel economy.

Installing an air fuel gauge is a popular modification that uses aftermarket parts. The average driver does not need to worry about adding an air fuel gauge to his or her car. Installation is straightforward and easy for the average DIY enthusiast to perform at home using basic hand tools.

If you have questions or concerns about air fuel ratio gauges or any of your vehicle's components, come into your local Pep Boys where we can answer any question, help you find any part, or perform any vehicle service you might need.