- Fuel pump: A weak fuel pump may not be able to deliver enough fuel to the engine at higher speeds.
- Fuel pressure regulator: A faulty fuel pressure regulator can cause the fuel pressure to be too low, which would also lead to a lean condition.
- Oxygen sensor: A bad oxygen sensor can send incorrect signals to the engine's computer, which could cause the computer to lean out the fuel mixture.
- Throttle body: A dirty throttle body can also restrict airflow to the engine, causing it to run lean.