FORD F-150 SPARK PLUG REPLACEMENT GUIDE
Applies to: 2015-2024 F-150 | 2.7L / 3.5L EcoBoost, 5.0L V8, 3.3L V6
1. Overview & Service Interval
– When to change: EcoBoost 60k miles, 5.0L V8 100k miles, sooner if tuned/towing/misfire
– Symptoms of bad plugs: Rough idle, P0300-P0308 misfire codes, poor MPG, hard start, shudder under boost
– Part Numbers:
– 3.5L EcoBoost: Motorcraft SP-594 (or NGK LTR6DI-8)
– 5.0L V8: Motorcraft SP-550 / SP-589
– 2.7L EcoBoost: SP-594
2. Tools & Materials Required
– Sockets: 7mm (coil bolt), 5/8″ spark plug socket magnetic, 3/8″ ratchet, 6″ & 10″ extension
– Measuring: Torque wrench (in-lbs), wire-type gap tool
– Consumables: 6 or 8 spark plugs, dielectric grease, brake cleaner, compressed air
– Safety: Safety glasses, gloves, cold engine only
3. Safety Precautions
– Engine must be COLD – Aluminum head threads strip when hot
– Disconnect Battery: Remove negative terminal to avoid coil short
– Clean First: Blow out dirt around coils with air — dirt falling in cylinder = engine damage
– Do Not Over-Torque: 9-11 ft-lbs only, over-torque will strip head
4. Step 1: Access Engine & Remove Engine Cover
– Open hood, remove plastic engine cover (pull straight up)
– For 3.5L EcoBoost: Remove intake tube bracket on driver rear for access to cylinder #5 & #6
5. Step 2: Remove Ignition Coils
– Disconnect: Press tab and unplug coil connector
– Unbolt: Remove 7mm coil retaining bolt
– Remove: Twist coil boot slightly, pull straight up
– Inspect: If oil in tube, valve cover gasket is leaking — fix first
6. Step 3: Remove Old Spark Plugs
– Insert 5/8″ plug socket with extension, break loose counter-clockwise
– Unscrew by hand, lift out
– Inspect Plug Condition:
– Light tan = Normal
– Black/wet = Rich fuel or oil burning
– White/blistered = Overheating / lean
– Heavy gap = Worn out
7. Step 4: Gap & Prepare New Spark Plugs
– Check Gap Specs:
– 3.5L / 2.7L EcoBoost: 0.028″ – 0.032″ (0.76mm) – Target 0.030″
– 5.0L V8: 0.049″ – 0.053″ (1.27mm) – Target 0.050″
– 3.3L V6: 0.049″ – 0.053″
– How to Gap: Only bend ground strap, never touch iridium center electrode
– Grease: Apply thin dielectric grease inside coil boot, NOT on plug threads
8. Step 5: Install New Spark Plugs
– Hand Thread First: Use extension by hand, turn backward 1/2 turn to catch threads, then clockwise
– Torque:
– All engines: 106-133 in-lbs (9-11 ft-lbs)
– EcoBoost: 115 in-lbs recommended
– Reinstall Coils: Torque coil bolt to 62 in-lbs (5 ft-lbs), reconnect harness until click
9. Step 6: Reassembly & Startup
– Reinstall engine cover and intake bracket
– Reconnect negative battery terminal
– Start engine, idle 2 minutes, listen for even idle
– Scan for codes, clear P0300 if present
– Test drive: 10 mins city + 1 hard pull (for EcoBoost) to check for misfire under boost
10. Final Checks & Pro Tips
– Always replace as full set – 6 for V6, 8 for V8
– Torque wrench is mandatory – feel is not enough on aluminum
– EcoBoost trick: If you still have misfire under boost after new plugs, gap down to 0.028″
– 2004-2008 5.4L Triton Warning: These have 2-piece plugs that break. Soak with PB Blaster overnight, use special Lisle extraction tool if breaks.