why does my Ford F-150 12th Generation (2009-2014) engine idle rough when cold

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, fuel pressure gauge, multimeter, cleaning supplies.
• Disconnect the negative battery terminal to prevent electrical shocks.
• Allow the engine to cool before starting work.

2. Check and Replace Spark Plugs

• Sub-steps:
  1. Remove the ignition coil covers (if applicable) and disconnect the ignition coils.
  2. Use a spark plug socket to remove the old spark plugs.
  3. Inspect the spark plugs for signs of wear or fouling; replace if necessary.
  4. Install new spark plugs, ensuring they are torqued to the manufacturer's specifications (typically around 13-15 ft-lbs).
  5. Reconnect the ignition coils.

3. Clean or Replace the IAC Valve

• Sub-steps:
  1. Locate the IAC valve (typically near the throttle body).
  2. Disconnect the electrical connector and remove the mounting screws to take off the IAC valve.
  3. Clean the valve with throttle body cleaner and a soft brush; if it appears damaged, replace it with a new unit.
  4. Reinstall the cleaned or new IAC valve and reconnect the electrical connector.

4. Inspect and Clean the Air Intake System

• Sub-steps:
  1. Remove the air intake duct and inspect the air filter; replace it if it's dirty.
  2. Clean the throttle body with a throttle body cleaner to remove carbon buildup.
  3. Reassemble the air intake duct and ensure all connections are secure.

5. Test Fuel Pressure

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail service port.
  2. Turn the ignition to the "ON" position without starting the engine to check the initial fuel pressure.
  3. Compare the reading to the manufacturer’s specifications (typically around 30-50 psi).
  4. If the pressure is low, check the fuel pump and fuel filter for issues.