- Clogged catalytic converter: A clogged catalytic converter can cause a lean condition by restricting the flow of exhaust gases. This can cause the engine to run rough and stall.
- Other vacuum leaks: In addition to the vacuum lines mentioned above, there are other areas where vacuum leaks can occur, such as the intake manifold gasket or the throttle body gasket.
- Faulty fuel pressure regulator: A faulty fuel pressure regulator can cause the fuel pressure to be too low, which can lead to a lean condition.
- Bad fuel pump: A bad fuel pump can cause the fuel pressure to be too low or inconsistent, which can lead to a lean condition.
- Defective oxygen sensor: If the oxygen sensor is defective, it can provide incorrect information to the engine computer, which can cause the engine to run lean.
- Faulty computer: In rare cases, the engine control unit (ECU) or computer may be faulty. If the computer is not functioning properly, it may not be able to correctly control the fuel mixture, which can lead to a lean condition.
