2021 GMC Acadia — Spark Plug Type, Gap & Torque Specs

Quick reference

Note: Never substitute spark plugs on late-model GM engines without confirming the exact part number by VIN. The table provides correct gap/torque/interval guidance, but part numbers vary by calibration and production date. Always check the underhood emissions label and GM/ACDelco catalog.

Why the right plug matters

• Heat range: Each Acadia engine (LSY 2.0T, LCV 2.5, LGX 3.6) was calibrated around a specific heat range. Too hot promotes pre-ignition; too cold causes fouling. Stick to the OE heat range for best drivability and knock control.
• Electrode metal:
  • Iridium: All 2021 Acadia engines ship with long-life iridium fine-wire plugs for strong spark at low voltage and excellent durability. These are designed for ~97,500-mile service under normal conditions.
  • Platinum: Acceptable in some aftermarket catalogs but usually not OE for this model year. If used, expect a shorter 60,000-mile interval and potentially different required gap.
  • Copper/nickel: Great conductivity but short life (around 30,000 miles). Not recommended on GDI/turbo applications like the 2.0T LSY.
• Engine management compatibility: Turbo and GDI systems are sensitive to plug design, resistor value, and projected tip length. Use the exact OE design or a verified equivalent from a reputable brand.

How to gap a spark plug

• Check, don’t force: Iridium fine-wire plugs are sold pre-gapped. Verify the gap with a wire-type feeler gauge. Avoid prying against the center electrode.
• Adjust lightly if needed: If a small correction is required, bend only the ground strap—use a gapping tool to make a slight tweak. Do not twist or touch the iridium center tip.
• Target gaps:
  • 2.0T LSY: 0.028 in (0.70 mm)
  • 2.5L LCV: 0.028–0.030 in (0.70–0.76 mm)
  • 3.6L LGX: 0.030 in (0.76 mm)

Replacement procedure tips (2021 GMC Acadia)

• Configuration: All 2021 Acadias use coil-on-plug (COP) ignition—no spark plug wires or distributor.
• Access:
  • Remove engine cover. On the transverse V6, the front bank is easy; the rear bank requires moving the intake ducting and working by feel or from the cowl side. The 4-cylinders offer straightforward access once the cover and any breather tubes are out of the way.
• Coil removal:
  • Disconnect the negative battery cable if desired for safety.
  • Unplug the coil electrical connector and remove the coil hold-down bolt (usually 10 mm). Twist the coil boot gently to break it free, then pull straight up.
• Prep the wells:
  • Blow out debris with compressed air before plug removal to keep grit out of the cylinder.
  • Use a 5/8 in spark plug socket with extension. Break loose and remove by hand once free.
• Installation:
  • Inspect new plugs, confirm gap.
  • Anti-seize: Not recommended on ACDelco nickel-plated shells. GM torque specs assume dry threads. If anti-seize is used against guidance, reduce torque ~20%, but the best practice is to install them dry on clean threads.
  • Thread by hand several turns to avoid cross-threading. Torque to 18 lb-ft (25 Nm) on aluminum heads.
  • Apply a small amount of dielectric grease inside each coil boot to ease future service and seal out moisture. Reinstall coils and connectors, then the engine cover.
• Reset and verify:
  • Clear any misfire codes if present and road test. A smooth idle and no misfire counters indicate success.

Known issues and notes

• Broken two-piece plugs (Ford 3-valve): Not applicable. The Acadia’s engines do not use the Ford 2-piece design that can seize and break.
• Ion-sensing coil requirements (some GM V8s): Not applicable here. The Acadia’s engines use conventional COP without the special ion-sensing requirement seen on certain 5.3L applications.
• Seized plugs: Any aluminum head can seize plugs if left in too long. Adhere to the 97,500-mile interval and service on a cool engine to avoid galling.
• Oil in plug wells: If you find oil in a coil boot, inspect the valve cover gasket or plug tube seals. Oil can carbon-track boots and cause misfires.
• Carbon and GDI: The 2.0T and 2.5L are gasoline direct-injected; keeping plugs fresh helps with cold starts and idle stability as injectors and valves accumulate normal deposits over time.

Need plugs replaced? Find a shop on Repairius.