When an engine starts but won't stay running, it is typically due to issues in one or more critical systems such as the fuel system, air intake, ignition system, or electronics. Common causes include:
- Fuel System Problems: A weak or faulty fuel pump, clogged fuel filter, or poor fuel quality can cause insufficient fuel delivery, making the engine stall shortly after starting.
- Air Intake Issues: A dirty or malfunctioning mass airflow (MAF) sensor, clogged air filter, vacuum leaks, or a dirty throttle body can disrupt the necessary air-fuel mixture.
- Ignition System Faults: Bad spark plugs, ignition coils, or problems with the ignition timing can cause the engine to lose spark and stall.
- Idle Air Control Valve Failure: If this valve fails, the engine may not maintain idle speed and shut off.
- Anti-Theft System Problems: Some vehicles shut off the engine shortly after start if the immobilizer or anti-theft system does not recognize the key.
- Battery or Alternator: A failing alternator can cause stalling once the battery's stored charge is used up after starting.
- Clogged Catalytic Converter: Though less common initially, it can cause power loss leading to stalling.
- Other Electrical or Sensor Issues: Problems with the Engine Control Unit (ECU) or related sensors can cause stalling.
- Engine Overheating: Older engines may shut down quickly to avoid damage if overheating occurs.
Actions to take include checking the fuel pump and filter, inspecting air filters and sensors (especially the MAF sensor), verifying spark plug and ignition coil conditions, and ensuring there are no obvious vacuum leaks. If the problem persists, a diagnostic scan using professional tools can identify specific sensor or ECU faults. Trying to keep the engine running by applying throttle at startup or turning off accessories like the A/C can sometimes help identify the cause.
