how to fix a misfire in my Toyota Highlander with code P0303

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface, and the engine is cool.
• Disconnect the negative battery terminal to ensure safety while working.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, gap gauge.
• Remove the engine cover if applicable.
• Locate the spark plug for cylinder 3.
• Use the socket set to carefully remove the spark plug.
• Inspect the old spark plug for wear; replace with a new spark plug if necessary.
• Set the gap on the new spark plug according to manufacturer specifications (typically around 0.043 inches for Toyota).
• Install the new spark plug, ensuring it is torqued to the manufacturer's specification (usually about 13 lb-ft).

3. Check and Replace Ignition Coil

• Tools Required: Socket set.
• Disconnect the electrical connector from the ignition coil on cylinder 3.
• Remove the bolt securing the ignition coil using the socket set.
• Pull the ignition coil out gently.
• Install the new ignition coil by reversing the removal process and securing it with the bolt. Reconnect the electrical connector.

4. Inspect and Test Fuel Injector

• Tools Required: Basic hand tools and optional fuel pressure gauge.
• Disconnect the fuel injector connector for cylinder 3.
• Using a multimeter, check the resistance of the fuel injector; it should be within the manufacturer's specified range (usually 12-16 ohms).
• If faulty, replace the fuel injector with a new one.
• Reconnect the fuel injector connector.

5. Perform Compression Test

• Tools Required: Compression tester.
• Remove the spark plug from cylinder 3.
• Insert the compression tester into the spark plug hole.
• Crank the engine for a few seconds and record the compression reading.
• Compare the reading with the manufacturer's specifications (typically around 180 psi for most Toyota engines). If low, further investigation into mechanical issues may be required.