How to Replace Spark Plugs in Your 2020 Ford Expedition

How to Fix Spark Plug Replacement

For 2020 Ford Expedition owners, spark plug replacement is a critical maintenance task that can resolve a host of performance issues, from rough idles to misfires. While the 2020 model's 3.5L EcoBoost engine has specific requirements, the principles of diagnosis and replacement are grounded in decades of owner experience. Ignoring worn plugs can lead to poor fuel economy, hard starting, and undue stress on expensive components like coil packs and catalytic converters. As one owner wisely advised regarding related components, "Inevitably, someone here will tell you to replace the COPs but if you're not having a problem I suggest leaving them alone. They are not a maintenance item despite popular belief and I think it's pure lunacy to spend ~$300-400 just for the heck of it." This guide will help you determine when to change your plugs, how to do it correctly, and how to avoid common pitfalls reported by other Expedition owners.

Symptoms

The symptoms of worn or failing spark plugs in your truck can range from subtle to severe. One of the most common reports is a rough idle, where the engine shakes or stumbles when stopped at a light. This is often coupled with a noticeable lack of power during acceleration, as if the truck is struggling to breathe. The check engine light will frequently illuminate, and a diagnostic scan will likely reveal specific misfire codes (like P0300, P0301, etc.), pointing directly to ignition issues.

In more advanced cases, you may experience hard starting. As one owner described a similar no-start scenario, "Didn't sputter at all just died. It will crank over but not start, fuel pump primes but I get no fuel pressure at the rail, just a tiny 'psssh' for a half a second but no fuel comes out at all." While this quote points to a fuel delivery issue, the symptom of cranking but not starting is shared with severe ignition failure. Another owner detailed intermittent problems: "Still starts up fine sometimes and idles OK, dies out after a long hard rev. Other times, it hard starts and cranks hard and just BARELY starts up and then runs super rough." This erratic behavior is a classic sign that one or more cylinders are not firing consistently.

Poor fuel economy is another silent symptom. As spark plugs erode and the gap widens, the spark becomes weaker and less efficient at completely igniting the air-fuel mixture. This leads to wasted fuel and a noticeable drop in miles per gallon. Finally, in extreme neglect, a persistent misfire can cause damage far beyond the spark plug itself. Unburned fuel can dump into the exhaust system, overheating and destroying the catalytic converter. One member noted, "Mike, we had another member that was chasing a misfire, and his turned out to be a clogged catalytic converter, go figure. I'd never heard of that causing a misfire like a coil, or faulty sparkplug." This highlights how a simple spark plug issue can cascade into a very expensive repair.

Most Likely Cause

The primary cause necessitating spark plug replacement is normal wear and erosion over time and mileage. Spark plugs are a consumable component. The electrodes slowly wear down with each ignition cycle, increasing the gap and requiring a higher voltage from the coil pack to create a spark. This increased electrical demand can eventually lead to coil pack stress and failure. The owner data shows plugs being replaced at high mileages, with one owner noting, "Current plugs have 126,000 miles (assuming they've never been changed) on them and the one I pulled so far doesn't look bad." Even if they "don't look bad," the specified service interval for the 2020 Expedition's EcoBoost engine is typically between 60,000 and 100,000 miles. Exceeding this interval is the most common reason for the symptoms described.

This wear is accelerated by underlying issues within the fuel system and related engine management components, as identified by owners. A dirty or malfunctioning Mass Air Flow (MAF) sensor, which owners cited as a cause, can cause the engine to run with an incorrect air-fuel ratio. A too-rich mixture (too much fuel) can foul plugs with carbon deposits, while a too-lean mixture (too little fuel) can cause the plugs to overheat. Furthermore, oil leaks from gaskets, like the valve cover or oil filter adapter, can allow oil to seep into the spark plug wells, contaminating the plugs and boots and causing misfires. An owner troubleshooting a rough idle found, "My oil filter adapter gasket was leaking, as well as the driver side breather tube being not fully connected on the valve cover." These kinds of leaks create an environment where new plugs will quickly fail again if the root leak isn't fixed.

How to Diagnose

Proper diagnosis ensures you're solving the right problem and not wasting money on unnecessary parts. Start by checking for diagnostic trouble codes (DTCs) with an OBD-II scanner. Codes in the P0300 range (random or cylinder-specific misfire) are your strongest direct evidence. Note the specific cylinder numbers if provided. Next, perform a visual and auditory inspection. With the engine running (in a well-ventilated area), listen for a rhythmic "puttering" or feel for excessive vibration, which indicates a misfire. You can also use an infrared thermometer to check the temperature of each exhaust manifold runner at the cylinder head; a cooler runner suggests that cylinder is not firing.

For a more hands-on test, you'll need a basic set of mechanic's tools. With the engine off and cool, remove the engine cover to access the coil-on-plug (COP) units. One at a time, carefully unplug the electrical connector and remove the bolt securing the coil pack. Pull the coil pack out of its well. Inspect the rubber boot for cracks, tears, or signs of oil contamination. If oil is present in the well, you have a leak from above (like a valve cover gasket) that must be addressed. To test further, you can swap the suspected bad coil pack with one from a known-good cylinder. Clear the codes, run the engine, and see if the misfire code follows the coil pack. If it does, the coil is faulty. If the misfire stays on the same cylinder, the problem is likely the spark plug itself or an issue like low compression or an injector problem.

As a final pre-replacement check, if you suspect a plug is seized—a common issue in older engines—owners have shared a useful tip. "I talked to my buddy that works at a dealership and he said if you have another vehicle to fill up the sparkplug holes with carb cleaner and let it sit overnight." This can help break down carbon and corrosion around the plug threads, making removal much safer and preventing the dreaded "broken plug" scenario. For the 2020 model, this is less common but a wise precaution if the plugs are significantly overdue.

Step-by-Step Fix

Replacing spark plugs on the 2020 Expedition's 3.5L EcoBoost V6 is a moderate DIY job that requires patience and the right tools. The engine uses a twin-turbo design, so access to the rear bank of plugs (closest to the firewall) can be tight. Allow 2-4 hours for a careful first-time job.

Step 1: Preparation. Ensure the engine is completely cold to prevent thread damage. Disconnect the negative battery cable for safety. Remove the engine cover by pulling up on the plastic retainers.

Step 2: Access the Coil Packs. You will need to remove several components for clear access. This typically includes the air intake tube assembly leading to the throttle body. For the rear bank, you may also need to unbolt and gently move the coolant overflow reservoir and possibly the windshield wiper cowl panel. Refer to a service manual for your specific model (XLT, Limited, Platinum) as configurations can vary. Label any connectors or hoses you disconnect.

Step 3: Remove Coil Packs. Using a 7mm or 8mm socket (confirm size), remove the bolt securing each coil pack. Gently wiggle and pull the coil pack straight up and out of its well. If it's stuck, use a dedicated coil puller tool or carefully twist with a flat-head screwdriver under the lip. As one owner shared regarding related work: "I was going to replace mine this time (coil replacement), but I got lucky and it was the front one on the driver side." This highlights the benefit of easy access to some cylinders.

Step 4: Remove Old Spark Plugs. This is the most critical step. First, use compressed air or a small vacuum to clean any debris from around the plug hole to prevent it from falling into the cylinder. Using a magnetic spark plug socket with a long extension and a swivel joint, carefully loosen each plug. Turn counterclockwise until the plug is free, then slowly lift it out. Inspect each old plug for signs of oil (leaking gasket), excessive carbon (rich fuel mixture), or white, blistered electrodes (overheating/lean condition).

Step 5: Gap and Install New Plugs. Your new plugs may be pre-gapped, but you must verify the gap with a feeler gauge tool. The correct gap for the 2020 Expedition 3.5L EcoBoost is critical; consult your owner's manual or the plug manufacturer (typically between 0.030-0.034 inches). Do not adjust platinum or iridium plugs by prying on the center electrode; adjust only by gently bending the ground electrode. Apply a tiny drop of anti-seize compound to the plug threads unless the plugs are specifically pre-coated. Hand-thread each plug into the hole to avoid cross-threading. Once hand-tight, use your torque wrench to tighten to the manufacturer's specification—usually between 15-20 ft-lbs. Over-torquing can crack the porcelain or damage the aluminum cylinder head threads.

Step 6: Reassemble. Apply a thin layer of dielectric grease inside the rubber boot of each new coil pack to prevent moisture intrusion and aid future removal. Reinstall each coil pack, ensuring it seats fully over the new plug. Reinstall the retaining bolt and reconnect the electrical connector. Reverse the steps you took for access, reinstalling the air intake, reservoir, and any other components. Reconnect the negative battery terminal.

Step 7: Test. Start the engine and let it idle. Listen for smooth operation. The idle may be slightly high as the engine computer relearns parameters; this should settle within a few minutes of driving. Take the truck for a gentle test drive, ensuring there is no hesitation or misfire under light acceleration.

Parts and Tools Needed

Using the correct parts and tools is essential for a successful, damage-free job.

Parts:

• Spark Plugs (6 required): Use only the OEM-specified type. For the 2020 3.5L EcoBoost, this is typically a Motorcraft SP-580 or SP-589 (platinum/iridium). Aftermarket equivalents like Autolite APP103 or XP103 are also mentioned by owners. One owner asked, "Any benefit or negatives over the APP103's?" Always verify the exact part number for your model.
• Dielectric Grease: A small tube for coating coil boot interiors.
• Anti-Seize Compound: A small amount of nickel-based anti-seize for plug threads (if not pre-coated).
• Optional but Recommended: New coil pack retaining bolts if any are rusty or damaged. A set of new coil pack boots if your originals are cracked or hardened.

Tools:

• Basic Socket Set (3/8" drive)
• Magnetic Spark Plug Socket (5/8" or 16mm) with a long extension (6 inches) and a swivel joint/u-joint
• Torque Wrench (inch-pounds or foot-pounds)
• Spark Plug Gap Feeler Gauge Tool
• 7mm or 8mm Socket for coil pack bolts
• Flat-Head Screwdriver (for prying clips, if needed)
• Compressed Air or Small Vacuum
• Nitrile Gloves and Safety Glasses

Real Owner Costs

The cost to replace spark plugs varies dramatically between DIY and professional service, and owner quotes provide clear real-world examples.

DIY Cost: The primary expense is the parts. An owner reported paying "~$55 for a set of 8 from Advance with a coupon." For your V6, a set of 6 high-quality plugs will typically cost between $45 and $90. If you need to purchase the specialty tools (torque wrench, swivel sockets), add a one-time investment of $75-$150. Therefore, a complete DIY job for a first-timer with tool purchase can range from $120 to $240. For subsequent changes with tools on hand, it's just the cost of the plugs.

Professional Mechanic Cost: Shop rates and parts markups increase the cost significantly. Dealerships will charge a premium for OEM parts and labor. The job typically takes 1.5-2.5 hours of labor. At an average rate of $120-$150 per hour, labor alone costs $180-$375. With parts marked up, the total bill at a dealership can easily range from $300 to $500 or more. This aligns with an owner's warning about unnecessary coil pack replacement: "it's pure lunacy to spend ~$300-400 just for the heck of it." That quote was for coils, but it illustrates the typical dealership price range for ignition system work. An independent shop may be $250-$400.

The savings for a competent DIYer are substantial, often over $200. However, if you encounter a seized plug or discover oil in the wells (indicating a valve cover gasket leak), the professional cost will rise to cover those additional repairs.

Prevention

Preventing premature spark plug failure revolves around adherence to maintenance schedules and addressing small problems before they cause damage.

First and foremost, replace your spark plugs at the manufacturer's recommended interval. For the 2020 Expedition, this is likely every 60,000 to 100,000 miles. Don't wait for symptoms to appear. Using the correct fuel grade (typically regular unleaded 87 octane is fine, but premium can be beneficial for performance in EcoBoost engines) helps prevent knock and plug overheating. Address any engine performance issues immediately. A persistent check engine light for something like a faulty MAF sensor or O2 sensor can lead to improper fueling and plug fouling. Remember the owner who found a "melted connector plug... for the passenger-side... O2 sensor"? Such electrical issues can disrupt the entire engine management system.

Vigilantly check for and repair engine oil leaks. As shown in the owner data, leaks from the valve cover gasket or oil filter adapter gasket can drip oil directly onto the spark plugs. Regularly inspect your engine bay for signs of oil seepage. Finally, when you do replace plugs, use high-quality parts (OEM Motorcraft or trusted equivalents like Autolite or NGK), torque them properly, and use dielectric grease. This ensures a reliable connection and protects against moisture, giving you a solid 60,000+ miles of trouble-free service.

What Owners Say

Real experiences from FORD owners:

Owner Experiences

"Didn't sputter at all just died. It will crank over but not start, fuel pump primes but I get no fuel pressure at the rail, just a tiny "psssh" for a half a second but no fuel comes out at all." — Amealey84 (source)

"Mike, we had another member that was chasing a misfire, and his turned out to be a clogged catalytic converter, go figure. I'd never heard of that causing a misfire like a coil, or faulty sparkplug." — 1955moose (source)

"Well, as the title says. My oil filter adapter gasket was leaking, as well as the driver side breather tube being not fully connected on the valve cover." — drokmofo (source)

Real Repair Costs

"I paid ~$55 for a set of 8 from Advance with a coupon. Inevitably, someone here will tell you to replace the COPs but if you're not having a problem I suggest leaving them alone." — ManUpOrShutUp (source)

"Inevitably, someone here will tell you to replace the COPs but if you're not having a problem I suggest leaving them alone. They are not a maintenance item despite popular belief and I think it's pure lunacy to spend ~$300-400 just for the heck of it." — ManUpOrShutUp (source)

FAQ

Q: How long does it take to replace spark plugs on a 2020 Expedition? A: For a first-time DIYer, plan for 2 to 4 hours, taking your time to ensure proper access and careful plug removal. A professional mechanic with the right tools and experience can typically complete the job in 1.5 to 2.5 hours.

Q: Can I drive my Expedition with a misfiring spark plug? A: It is not recommended. Driving with a persistent misfire can cause unburned fuel to enter the exhaust system, which can overheat and destroy the expensive catalytic converter. It also stresses the remaining coil packs, can damage the oxygen sensors, and significantly reduces fuel efficiency and power. As one owner's experience indicated, a misfire can even be a symptom of a clogged catalytic converter, creating a vicious cycle of damage.

Q: Is spark plug failure a common issue on the 2020 Expedition? A: Spark plug wear is a common maintenance item on all vehicles, not a specific defect of the 2020 Expedition. The 3.5L EcoBoost engine is generally reliable in this regard. The "common issue" is owners exceeding the recommended service interval, which leads to the symptoms described. The design is less prone to the plug breakage problems that plagued some older Ford V8 engines.

Q: Should I replace the coil packs (COPs) at the same time as the spark plugs? A: Not necessarily. Coil-on-plug units are not a standard maintenance item. As an owner strongly advised, "if you're not having a problem I suggest leaving them alone." If your truck is running smoothly with no misfire codes, replacing functional coils is an unnecessary expense. However, if one coil fails, it's not unreasonable to replace the others as a set, especially at higher mileages (e.g., over 150k), but it is not required. Always diagnose a misfire to confirm the cause is the coil before replacing it.

Q: What is the risk of breaking a spark plug during removal on this model? A: The risk is very low on the 2020 Expedition with the 3.5L EcoBoost engine. The notorious "broken plug" issue was associated with the older 3-valve 5.4L and 4.6L V8s. The modern engine uses a different plug design and thread type. The primary risk is cross-threading the new plug during installation if you don't start it by hand, or over-torquing it. Always use a torque wrench.

Q: I have a rough idle after doing other work. Could it be related to the spark plugs? A: Absolutely. If you recently had work done in the engine bay, it's possible a coil pack connector was not fully snapped back on, or a vacuum line (like a breather tube) was disturbed. An owner found this exact cause: "My oil filter adapter gasket was leaking, as well as the driver side breather tube being not fully connected on the valve cover." Always double-check all connections related to the ignition system and intake after any service.