There are several potential reasons why your 2008 Lexus RX 350 is stalling, especially when the air conditioner is on. Stalling can be caused by various issues related to the engine, fuel system, or electrical components. Here are some common causes to consider:
Idle Air Control Valve (IACV) malfunction: The IACV regulates the engine's idle speed. If it becomes dirty or malfunctions, it may not adjust the idle speed properly when the air conditioner is engaged, leading to stalling.
Dirty or faulty Mass Air Flow (MAF) sensor: The MAF sensor measures the amount of air entering the engine and helps adjust the fuel-air mixture accordingly. If it's dirty or malfunctioning, the engine may not receive the correct air-fuel ratio, causing stalling.
Faulty or clogged EGR (Exhaust Gas Recirculation) valve: The EGR valve recirculates a portion of the exhaust gases back into the engine to reduce emissions. If it's stuck open or clogged, it can cause stalling, especially when the AC is on.
Weak fuel pump or fuel filter: A weak fuel pump or a clogged fuel filter can restrict the flow of fuel to the engine, leading to insufficient fuel supply and stalling, especially when there is an additional load from the air conditioner.
Faulty ignition system: Issues with spark plugs, ignition coils, or spark plug wires can cause misfires and stalling when the air conditioner is engaged.
Vacuum leak: A vacuum leak in the engine's intake system can disrupt the air-fuel mixture and lead to stalling, especially under increased load from the air conditioner.
Electrical issues: Problems with the electrical system, such as a faulty alternator or battery, can cause fluctuations in voltage, affecting the engine's performance and causing stalling.
Overheating: Running the air conditioner puts additional load on the engine, and if the cooling system is not functioning correctly, the engine may overheat, leading to stalling.
To pinpoint the exact cause of the stalling issue, it's best to have the vehicle diagnosed by a qualified mechanic or a Lexus dealership. They can perform a comprehensive inspection, scan for error codes using a diagnostic tool, and conduct various tests to identify the underlying problem. Once the issue is identified, appropriate repairs or replacements can be made to resolve the stalling problem.