* Low Battery Voltage/Charging System Issues: The AC compressor requires a significant amount of power. A weak battery, failing alternator, or corroded connections can cause voltage to drop significantly when the compressor kicks in, leading to the engine stalling. This is often the *most common* cause. Have the battery and charging system tested.
* Insufficient Fuel Pressure: The extra load from the AC compressor can exacerbate existing fuel delivery problems. A weak fuel pump, clogged fuel filter, or issues within the fuel injection system itself might not be able to supply enough fuel under the increased demand.
* Vacuum Leaks: The AC system uses vacuum in some aspects (e.g., for the HVAC control system). A significant vacuum leak somewhere in the engine's intake system could cause the engine to stumble or stall under the added load of the AC.
* Faulty Idle Air Control (IAC) Valve: The IAC valve regulates airflow at idle to maintain a consistent engine speed. If it's dirty, malfunctioning, or sticking, it might not be able to compensate for the additional load from the AC, causing the engine to stall.
* Throttle Position Sensor (TPS) Problem: An inaccurate TPS reading can affect the fuel/air mixture, leading to stalling, especially under increased load.
* Engine Cooling System Issues: While less likely to directly cause immediate stalling, overheating can indirectly lead to problems. If the cooling system is compromised, the engine might overheat quickly under the added strain of the AC, causing it to shut down as a safety measure.
Troubleshooting Steps:
1. Check the Battery and Charging System: This is the first and most important step. Have a mechanic or auto parts store test your battery and alternator.
2. Inspect Vacuum Lines: Visually inspect all vacuum lines for cracks, leaks, or disconnections.
3. Check the Fuel System: A mechanic can test fuel pressure to see if it's sufficient under load. Replacing the fuel filter is a relatively inexpensive first step.
4. Clean the IAC Valve: This is a relatively easy DIY repair, though a proper cleaning procedure is necessary.
5. Inspect the TPS: This sensor might need to be tested with a multimeter or replaced if faulty.
Important Note: These are potential causes, and diagnosing the exact problem requires a systematic approach, possibly involving diagnostic tools and a trained mechanic. Simply adding more gas won't fix any of these underlying problems.
