1. Idle Air Control (IAC) Valve: This valve regulates the amount of air entering the engine at idle. A malfunctioning IAC can cause the engine to stall, especially when the engine speed drops during braking. Dirty or sticking IAC valves are a common cause.
2. Crankshaft Position Sensor (CKP): This sensor tells the engine's computer the position of the crankshaft. A faulty CKP sensor can lead to erratic engine operation and stalling, particularly under load (like braking).
3. Throttle Position Sensor (TPS): The TPS tells the computer the position of the throttle. A faulty TPS can provide incorrect information, causing the engine to miscalculate fuel and air mixtures, resulting in stalling.
4. Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can lead to incorrect fuel mixtures and stalling.
5. Battery/Alternator Issues: A weak battery or failing alternator can cause voltage drops, leading to the engine shutting off, especially under load. Check the battery voltage and the alternator's output.
6. Fuel Pump: While less likely, a failing fuel pump might struggle to provide sufficient fuel when engine speed drops during braking. This is more likely to manifest as hesitation or sputtering before stalling.
7. Vacuum Leaks: Leaks in the vacuum system can disrupt the engine's operation, potentially causing stalling.
8. PCM (Powertrain Control Module) Issues: In rare cases, a problem with the PCM (the engine's computer) itself could be responsible. This is usually diagnosed after ruling out other possibilities.
Troubleshooting Steps:
1. Check the battery terminals: Ensure they are clean, tight, and corrosion-free.
2. Test the battery voltage: Should be around 12.6V when the engine is off and around 13.5-14.5V when running.
3. Inspect the engine for any obvious vacuum leaks: Look for loose hoses or cracks.
4. Check the engine's air filter: A clogged filter can restrict airflow and cause stalling.
5. Have a professional mechanic diagnose the problem: This is often the best course of action. They have the tools and expertise to accurately pinpoint the issue. They can perform diagnostics using a scan tool to read trouble codes from the vehicle's computer.
Important Note: Driving a vehicle with this problem is risky. The engine stalling while braking could lead to a dangerous situation. Have it checked by a mechanic as soon as possible.
