my Toyota Corolla E170 (2013-2019) has a rough idle, especially when cold

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Replace Spark Plugs

• Remove the engine cover (if applicable).
• Use a spark plug socket and ratchet to carefully remove each spark plug.
• Inspect the spark plugs for wear and carbon buildup.
• Replace with new spark plugs that meet OEM specifications.
• Torque the new spark plugs to the manufacturer’s specifications (usually around 13-20 lb-ft).

3. Clean the Throttle Body

• Remove the intake air duct to access the throttle body.
• Use throttle body cleaner and a soft brush to clean the throttle body, being careful not to damage the throttle plate.
• Reassemble the intake duct and ensure all clamps are tight.

4. Test and Replace Ignition Coils (if necessary)

• Remove the ignition coils from the spark plugs.
• Inspect for signs of damage or wear.
• Test the resistance of the ignition coils with a multimeter; replace any that are out of specification.
• Reinstall the ignition coils securely.

5. Check and Clean the MAF Sensor

• Disconnect the MAF sensor connector and remove it from the intake.
• Use MAF sensor cleaner to clean the sensor elements carefully.
• Reinstall the MAF sensor ensuring it’s secured properly.

6. Fuel System Inspection

• Connect a fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position without starting the engine to check fuel pressure.
• If the pressure is low, inspect the fuel filter and fuel pump for issues; replace as necessary.