Fuel System:
* Low fuel: Sounds obvious, but a low fuel level can sometimes cause erratic behavior.
* Fuel pump: A failing fuel pump may not be supplying enough fuel, especially when the engine is under low demand at idle.
* Fuel filter: A clogged fuel filter restricts fuel flow, leading to similar symptoms.
* Dirty fuel injectors: Clogged or dirty injectors can prevent proper fuel delivery.
Ignition System:
* Spark plugs: Worn or fouled spark plugs can cause misfires, especially at idle.
* Ignition coil: A failing ignition coil can lead to misfires in one or more cylinders.
* Distributor cap and rotor (older vehicles): These components can wear out and cause poor ignition.
Air Intake System:
* Vacuum leak: A leak in the vacuum system can disrupt the air-fuel mixture, causing stalling.
* Mass airflow sensor (MAF) issues: A faulty MAF sensor provides inaccurate readings to the engine computer, leading to poor fuel mixture.
* Dirty air filter: A severely clogged air filter restricts airflow, affecting the air-fuel mixture.
Engine Management System:
* Idle air control valve (IACV): This valve regulates air flow at idle. A malfunctioning IACV can cause stalling or rough idling.
* Throttle position sensor (TPS): A faulty TPS provides inaccurate throttle position information to the engine computer.
* Engine control module (ECM) / Powertrain Control Module (PCM): A failing ECM/PCM is less common but can cause a wide range of problems, including stalling.
* Sensors: Many other sensors (e.g., crankshaft position sensor, camshaft position sensor) can cause stalling if they fail and provide inaccurate readings to the engine.
Other Possibilities:
* Alternator: A failing alternator might not be charging the battery adequately, leading to stalling when the battery is low.
* Battery: A weak or failing battery can also cause the engine to stall.
* Transmission problems (automatic): In automatic transmissions, issues with the torque converter or other components can cause stalling or rough idling.
Troubleshooting Steps:
It's important to have a mechanic diagnose the problem, but some initial checks you can do include:
* Check your engine oil and coolant levels.
* Inspect your battery terminals for corrosion.
* Check the air filter for cleanliness.
Ignoring this problem can lead to more serious damage, so it's best to get it checked out by a qualified mechanic as soon as possible. They have the tools and expertise to properly diagnose the underlying cause.
