2015-2019 Ford Explorer — Replace Spark Plugs

1

Cool the engine (verify your engine!)

The 2015–2019 Ford Explorer uses different plugs by engine — verify YOUR engine. 2.3T EcoBoost: Motorcraft SP-594, gap 0.028–0.030", torque unverified (check manual). 3.5L V6: Motorcraft SP-520, gap 0.051", torque 133 in-lbs. Note: the 2015 XLT may be the 2.0T — confirm your engine before buying plugs. This guide covers the 2.3T and 3.5L (verify which you have). The 0.028" turbo gap vs 0.051" V6 gap are very different — using the wrong gap causes misfires. You'll need: correct Motorcraft plugs for your engine, spark plug socket, extensions, intake gasket (3.5L). Critical: let the engine cool. The 3.5L's plenum must come off (see below).

🔧 Mechanic's note — Ray Delgado

I verify the engine before buying plugs — the 2.3T and 3.5L take completely different gaps, and I've seen the wrong plugs cause immediate misfires.

2

Access coils (3.5L plenum off for rear)

Remove the engine cover. Both engines use coil-on-plug. For the 2.3T EcoBoost (inline-4 turbo): the coils are on top — relatively accessible, though the turbo plumbing crowds the bay. For the 3.5L V6: the front bank is accessible, but the REAR bank is under the intake plenum — you MUST remove the plenum (89 in-lbs + 45° on reinstall). Disconnect intake tubing, unbolt the plenum, label everything. Plan for a new plenum gasket. The 3.5L's plenum is the big job.

3

Remove one coil at a time

For the 2.3T: the turbo heat ages the boots — inspect carefully. For the 3.5L rear bank (after plenum removal): work against the firewall. The Explorer's coils are reliable — but the 2.3T's turbo heat is hard on boots.

4

Remove the old spark plug

Remove the old Motorcraft plug. 2.3T: the old SP-594 should show turbo wear; the tight 0.028–0.030" gap is critical for the EcoBoost — if eroded wider, that's your misfire. 3.5L: the old SP-520 at 0.051" is a wide gap (naturally aspirated V6). If a 3.5L plug is oil-fouled, check the valve covers. For the 3.5L rear bank, use long extensions. Don't drop debris into the cylinders or intake ports. Verify you have the correct plug for your engine — the gaps differ hugely.

5

Gap and hand-thread the new plug

New plugs come pre-gapped — verify but don't adjust (precious metal). 2.3T: 0.028–0.030" (tight turbo gap). 3.5L: 0.051" (wide NA gap). Hand-thread the new plug until it seats. NEVER wrench-start — aluminum heads. For the 3.5L rear bank: hand-thread blind against the firewall. If it binds, back out. Ensure correct plug: SP-594 for 2.3T, SP-520 for 3.5L. The wrong gap (0.028" in a 3.5L, or 0.051" in a 2.3T) causes immediate misfires.

6

Torque to specification

Torque to spec. 3.5L: 133 in-lbs (inch-pounds, not ft-lbs!). 2.3T: torque unverified — check your Ford service manual (do not guess). Use a torque wrench. For the 3.5L, the 133 in-lbs is ~11 ft-lbs — don't confuse the units. The 2.3T's turbo needs correct torque — loose plugs blow out under boost. When in doubt for the 2.3T, consult the manual. Do not over-torque either engine's aluminum heads.

7

Reinstall coils (and 3.5L plenum)

For the 3.5L: reinstall the intake plenum with a NEW gasket. Torque the plenum bolts to 89 in-lbs + 45° (torque-to-yield — follow the sequence). For the 2.3T: reinstall any turbo plumbing you moved.

8

Reassemble and test

Reinstall the engine cover. Start the engine — it should idle smoothly (the 2.3T has turbo character, the 3.5L V6 is smooth). Check for misfire codes. The Explorer's plug job depends on your engine: the 2.3T's tight 0.028" gap is critical for boost, the 3.5L's 0.051" is for the NA V6. If you have the wrong gap, you'll misfire immediately. Test drive: verify smooth power. Remember: 2015 XLT may be the 2.0T (different plugs) — confirm your engine. The 2.3T and 3.5L use different Motorcraft plugs (SP-594 vs SP-520) — don't mix them.

🔧 Mechanic's note — Tom Becker

I check for misfire codes before the test drive — if the gap's wrong it'll misfire immediately, and I've learned to suspect the plugs before the coils.