Phase 1: The Easy Checks (Before you dive into expensive parts)
1. Visual Inspection:
* Spark Plugs: Check the spark plugs in cylinder #1 for fouling, breakage, or wear. Replace them if necessary. This is the cheapest and easiest fix, and often solves the problem. While you're at it, consider replacing all eight plugs for consistency.
* Ignition Wires (Coil Packs): Inspect the ignition wire (or coil pack boot) for cylinder #1 for cracks, damage, or loose connections. Look for signs of arcing or burning. Replace any damaged components. Again, check all wires/boots for good measure.
* Vacuum Leaks: Visually inspect all vacuum hoses and connections near the intake manifold and cylinder #1 area for cracks, leaks, or loose connections. A vacuum leak can disrupt the air/fuel mixture.
* Fuel Injector: While difficult to visually inspect, make sure the injector connector is securely attached. A loose or damaged connector can cause a misfire.
2. Basic Testing:
* Check Engine Oil: Low oil level can lead to a misfire.
* Check Engine Compression: A compression test will tell you if there's a problem with the cylinder itself (valves, piston rings, etc.). Low compression in cylinder #1 strongly points to internal engine issues. A compression test is crucial in this step.
* Swap Ignition Coil: If you have a spare coil pack, swap the one for cylinder #1 with another cylinder's coil pack. If the code follows the coil pack, you've found the culprit.
Phase 2: If the Easy Checks Fail
If the basic checks don't solve the problem, you'll need more advanced diagnostics:
1. Further Fuel System Checks:
* Fuel Injector Test: A fuel injector test will confirm if the injector for cylinder #1 is delivering the correct amount of fuel. This usually requires a specialized fuel pressure gauge and potentially a scan tool capable of monitoring injector pulse width.
* Fuel Pressure Test: Low fuel pressure can cause misfires. This requires a fuel pressure gauge.
2. More Advanced Ignition System Checks:
* Ignition Coil Testing (if no spare): If you didn't swap coils, you might need to test the coil pack itself with a multimeter to check its resistance and ensure it's functioning correctly.
3. Internal Engine Issues:
* Valve Problems: If the compression test reveals low compression, it could indicate a problem with the valves (burnt, bent, etc.). This requires more in-depth diagnostics and likely a professional mechanic.
* Piston Problems: Similar to valve problems, piston issues (rings, damage) require professional attention and are much more serious.
Important Considerations:
* Professional Diagnosis: If you're not comfortable performing these checks, it's best to take your Expedition to a qualified mechanic. Incorrect diagnosis and repair can lead to further damage.
* Scan Tool: A more advanced scan tool might provide more detailed information about the misfire, such as the number of misfires, the conditions under which they occur (idle, acceleration, etc.), which can aid in diagnosis.
* Multiple Codes: Pay attention to any other trouble codes that might be present. They can provide valuable clues to the underlying issue.
Remember safety first! Disconnect the negative battery terminal before starting any electrical work. If you're unsure about any of these steps, don't hesitate to consult a repair manual or seek professional help. A faulty cylinder #1 can lead to significant damage if ignored.
