my Ford F-150 has a rough idle when cold, what could be causing it?

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to ensure safety while working on electrical components.
• Allow the engine to cool before starting any work.

2. Inspect and Replace Spark Plugs

• Remove the ignition coil from each spark plug by unscrewing the mounting screws.
• Use a spark plug socket to carefully remove the old spark plugs.
• Inspect the old spark plugs for signs of wear (e.g., fouling, excessive gap).
• Install new spark plugs, ensuring the gap is set to manufacturer specifications (typically around 0.054 inches for F-150).
• Reinstall the ignition coils and secure them with the screws.

3. Clean the Throttle Body

• Remove the air intake duct connected to the throttle body.
• Use throttle body cleaner and a clean rag to remove carbon buildup inside the throttle body.
• Ensure the throttle plate opens and closes freely without sticking.
• Reattach the air intake duct securely.

4. Replace Fuel Filter (if necessary)

• Locate the fuel filter and relieve fuel system pressure by removing the fuel pump fuse and running the engine until it stalls.
• Disconnect the fuel lines from the filter, being careful to catch any spilled fuel.
• Install the new fuel filter, ensuring the fuel flow direction matches the markings on the filter.
• Reconnect the fuel lines securely.

5. Check Engine Coolant Temperature Sensor

• Locate the coolant temperature sensor and disconnect the electrical connector.
• Use a multimeter to test the resistance of the sensor and compare it to manufacturer specifications.
• If the sensor is faulty, remove it using a socket wrench and install a new sensor.