my Toyota Corolla E170 (2013-2019) has a P0301 misfire code, what should I check first?

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shock.
• Allow the engine to cool down before starting work.

2. Inspect and Replace Spark Plug

• Tools Required: Spark plug socket, ratchet, torque wrench.
• Remove the ignition coil cover (if applicable) to access the spark plug.
• Use a spark plug socket to remove the spark plug from cylinder 1.
• Inspect the spark plug for wear, carbon buildup, or damage.
• If necessary, replace the spark plug with a new one, ensuring it is gapped correctly (typically 0.043 inches for a Corolla).
• Torque the new spark plug to the manufacturer's specification (typically around 13 lb-ft).

3. Check and Replace Ignition Coil

• Tools Required: Socket set.
• Disconnect the electrical connector from the ignition coil for cylinder 1.
• Remove the coil by unscrewing it from the cylinder head.
• Inspect the coil for cracks or carbon tracking.
• If defective, replace the ignition coil with a new one, ensuring proper seating and reconnecting the electrical connector.

4. Test Fuel Injector

• Tools Required: Fuel pressure gauge, cleaning kit (if needed).
• Disconnect the fuel injector connector for cylinder 1.
• Use a fuel pressure gauge to check fuel pressure at the rail to ensure adequate supply.
• If the injector is suspected of being clogged, clean it using a fuel injector cleaning kit or replace it if necessary.

5. Perform Compression Test

• Tools Required: Compression gauge.
• Remove the spark plug for cylinder 1.
• Insert the compression gauge into the spark plug hole.
• Crank the engine for several revolutions and note the compression reading.
• Compare the reading to the manufacturer's specifications (typically around 180 psi for a healthy engine). If the compression is low, further investigation of the piston rings or valves might be required.