* Idle Air Control (IAC) Valve: This valve regulates the amount of air entering the engine at idle. A dirty or malfunctioning IAC valve can cause rough idling, stalling, and shaking, especially when the car is stopped. This is a common issue and relatively inexpensive to replace.
* Mass Airflow Sensor (MAF) Sensor: This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can provide inaccurate readings, leading to a lean or rich fuel mixture, causing rough running and stalling. Cleaning it (carefully, following instructions) is often the first step; replacement may be necessary.
* Throttle Position Sensor (TPS): This sensor tells the computer the position of your throttle. A faulty TPS can cause erratic engine behavior, including stalling.
* Spark Plugs and Wires: Worn-out spark plugs or damaged ignition wires can cause misfires, resulting in shaking and stalling. These are relatively easy and inexpensive to check and replace.
* Fuel System Issues: Although less likely without a check engine light, a problem with the fuel pump, fuel filter, or fuel injectors could contribute. A weak fuel pump might not deliver enough fuel when the engine is idling. A clogged filter restricts fuel flow. Faulty injectors can cause inconsistent fuel delivery.
* Vacuum Leaks: A leak in the vacuum system can disrupt the engine's operation, leading to erratic idling and stalling. These can be tricky to find.
* Transmission Issues (Less Likely): While less likely given the description, a problem with the transmission's torque converter could theoretically cause shaking and stalling, although you'd probably notice other symptoms as well.
What to do:
1. Check the obvious: Start with the easiest and cheapest checks: Inspect spark plugs and wires for damage or wear. If you're comfortable, try cleaning the MAF sensor (with MAF sensor cleaner, NOT regular cleaner!).
2. Professional Diagnosis: Since you've eliminated the obvious and the check engine light isn't on, taking your car to a mechanic for a proper diagnosis is the best course of action. A mechanic can perform tests to identify the faulty component. They have tools (like a scan tool that can read more than just the check engine light codes) and the expertise to pinpoint the problem effectively. Mention the symptoms specifically, including the lack of a check engine light.
Don't continue driving the car if it's stalling unpredictably, as this could lead to a dangerous situation.
