2019 BMW X3 G01 - Rough Idle and Check Engine Light (P030x)

A rough idle accompanied by a Check Engine Light and P030x codes (P0300 - Random/Multiple Cylinder Misfire Detected, P0301 - Cylinder 1 Misfire, P0302 - Cylinder 2 Misfire) strongly indicates an engine misfire. Given your 2019 BMW X3 xDrive30i (G01) with 60k miles, this is a common mileage for certain maintenance items to cause such issues.

Here are the most likely culprits and troubleshooting steps:

1. Spark Plugs:

   • Cause: Spark plugs are a primary suspect for misfires, especially around 60k miles. They wear out, leading to a weak or inconsistent spark.
   • DIY Check/Fix: If you're comfortable, replacing spark plugs is a common DIY task. Ensure you use BMW-approved plugs and torque them correctly. Start with the cylinders showing specific misfire codes (Cylinder 1 and 2 in your case).

2. Ignition Coils:

   • Cause: Ignition coils provide the high voltage to the spark plugs. They can fail individually, leading to misfires in specific cylinders. Sometimes, one failing coil can put stress on others.
   • DIY Check/Fix: You can try swapping an ignition coil from a misfiring cylinder (e.g., Cylinder 1) to a non-misfiring cylinder (e.g., Cylinder 3). Clear the codes, drive the car, and re-scan. If the misfire code moves to Cylinder 3 (P0303), then the coil is likely faulty.

3. Fuel Injectors:

   • Cause: A clogged or faulty fuel injector can prevent a cylinder from getting enough fuel, causing a misfire. This is less common than plugs or coils but still possible.
   • DIY Check/Fix: This is harder to diagnose at home without specialized tools. You might try a fuel system cleaner, but if the injector is truly faulty, it will need replacement.

4. Vacuum Leaks:

   • Cause: Unmetered air entering the engine can lean out the air/fuel mixture, leading to misfires, especially at idle. Look for cracked hoses or loose connections.
   • DIY Check/Fix: Visually inspect all vacuum lines and intake components for cracks or disconnections.

Troubleshooting Steps:

• Start with the easiest and most common: Replace spark plugs first, especially for the cylinders showing misfires. If that doesn't resolve it, move to swapping ignition coils.
• Clear Codes: After each step, clear the OBD codes and drive the car to see if the Check Engine Light returns and if the misfire codes persist or change.

When to See a Shop: If replacing spark plugs and swapping ignition coils doesn't resolve the issue, or if you're uncomfortable performing these tasks, it's best to take your X3 to a qualified BMW specialist. They have advanced diagnostic equipment (like ISTA) to perform a comprehensive diagnosis, including fuel injector testing, compression tests, and smoke tests for vacuum leaks, ensuring an accurate and efficient repair. Driving with persistent misfires can damage your catalytic converter over time.