* Dirty or Failing Throttle Position Sensor (TPS): The TPS tells the engine's computer the throttle's position. A dirty or faulty TPS can provide inaccurate information, leading to a rough start and hesitation until it gets a clearer signal. This is very common on older vehicles.
* Mass Airflow Sensor (MAF) Issues: Similar to the TPS, the MAF sensor measures the amount of air entering the engine. A dirty or malfunctioning MAF sensor can cause a lean air/fuel mixture, leading to hesitation.
* Idle Air Control (IAC) Valve: This valve controls the engine's idle speed. If it's dirty or sticking, it can cause rough idling and hesitation, especially when cold.
* Fuel System Problems: A clogged fuel filter or low fuel pressure can cause a hesitant start. Although less likely to only last a few seconds, it's worth considering, especially if the hesitation is accompanied by poor acceleration even after the initial few seconds.
* Spark Plugs and Wires: Worn-out spark plugs or faulty ignition wires can cause misfires, leading to hesitation. This is more likely to cause ongoing problems rather than just a brief hesitation, but it's a possibility.
What to do:
1. Check the easy things first: Make sure your battery is fully charged and the terminals are clean and tight. A weak battery can cause similar symptoms.
2. Clean the MAF sensor: This is relatively easy to do yourself (look up a tutorial specific to your Impala's year). Use MAF sensor cleaner, *not* brake cleaner or other solvents. Be gentle and avoid touching the sensor element.
3. Clean the throttle body: Often done in conjunction with cleaning the MAF. You'll likely need a throttle body cleaner and some rags. Again, look up a YouTube video specific to your car model.
4. Check the IAC valve: This might require some disassembly, so it's a bit more involved, and you might need to replace it rather than just clean it, depending on its condition.
5. Consider fuel system diagnostics: If cleaning the MAF and throttle body doesn't help, you might need to have a mechanic check fuel pressure and filter condition.
If you're not comfortable working on your car yourself, take it to a mechanic. They can diagnose the problem accurately and perform the necessary repairs. Describe the problem precisely as you did here – it will help them troubleshoot effectively. Mentioning the short duration of the hesitation is key.
