* Mass Airflow Sensor (MAF): This is arguably the most important sensor for fuel economy. It measures the amount of air entering the engine. The computer uses this information to calculate the correct amount of fuel to inject. A faulty MAF sensor can lead to a rich or lean fuel mixture, drastically reducing gas mileage.
* Throttle Position Sensor (TPS): This sensor tells the computer the position of the throttle plate. An inaccurate reading can cause incorrect fuel delivery, affecting performance and fuel economy.
* Oxygen Sensor(s) (O2): Usually, there are multiple O2 sensors (one upstream and one downstream of the catalytic converter). They monitor the exhaust gases to determine the air/fuel mixture's efficiency. Faulty O2 sensors prevent the computer from making necessary adjustments to optimize the mixture, leading to poor fuel economy.
* Manifold Absolute Pressure (MAP) Sensor: This sensor measures the pressure in the intake manifold. The computer uses this information, along with the MAF sensor reading, to determine the engine load and calculate fuel delivery. A bad MAP sensor will lead to inaccurate fuel calculations.
* Crankshaft Position Sensor (CKP): While not directly involved in fuel calculations, a faulty CKP sensor can disrupt ignition timing, leading to misfires and reduced fuel efficiency.
* Temperature Sensors (Coolant Temperature Sensor, Intake Air Temperature Sensor): These sensors provide crucial information about engine temperature and air temperature. Incorrect temperature readings can lead to incorrect fuel delivery strategies, negatively impacting fuel economy.
Indirect Effects: While not directly measuring air/fuel ratios, sensors related to emissions control (like the catalytic converter itself) can indirectly affect gas mileage if malfunctioning. A clogged or failing catalytic converter will restrict exhaust flow, potentially impacting engine performance and reducing fuel economy.
Important Note: A diagnostic trouble code (DTC) scan using an OBD-II scanner is the best way to diagnose problems with these sensors. A simple code reader can often identify any sensor-related fault codes. Don't just replace sensors randomly; addressing the actual problem indicated by the codes is crucial for effective repair.
