2025 GMC Acadia — Spark Plug Type, Gap & Torque

Quick reference

Why the right plug matters

Choosing the correct spark plug is critical to performance and durability—especially on a modern direct-injected turbo engine like the Acadia’s 2.5L LKO. The factory uses a fine-wire iridium plug for stable spark at high cylinder pressures, fast cold starts, and long life.

• Heat range: Too hot a plug can trigger pre-ignition/knock under boost; too cold can foul at idle and low load. The LKO is calibrated for a specific heat range—stick with OE or an exact cross-reference.
• Electrode material:
  • Iridium: Best for this engine. Finest wire, strongest spark, and the longest life (typically 100k miles). Resists erosion under turbocharged pressures.
  • Platinum: Acceptable only if it’s an OE-approved cross for this engine, but service life is shorter (often ~60k miles).
  • Copper/nickel: Strong initial spark but short life (~30k miles) and not recommended for modern DI turbos.
• Construction and resistance: GM’s ignition strategy expects resistor-type fine-wire plugs. Non-resistor or mismatched designs can cause radio interference, misfire counts, or rough running.

Note on part numbers: GM supplies the 2025 Acadia 2.5T plug under an ACDelco GM Genuine Iridium part that is cataloged by VIN. Because applications change mid-year, always verify the exact PN through a GM/ACDelco catalog with your VIN rather than substituting. Avoid mixing brands/part numbers across cylinders.

How to gap a spark plug

Most iridium plugs are pre-gapped, but always verify before installation.

1. Measure: Use a round-wire gap gauge. Slide the electrode over the correct thickness (0.028 in / 0.70 mm) and feel for a light drag.
2. Adjust lightly: If needed, bend only the ground strap. Support the strap and nudge it—never pry on or against the fine iridium center electrode.
3. Recheck: Measure again in multiple spots to confirm a consistent gap. If a plug uses a “no-adjust” specification from the manufacturer, replace rather than forcing an adjustment.

Replacement procedure tips (2.5L Turbo I4 LKO)

The LKO uses coil-on-plug ignition with the plugs centered in the cam cover.

• Access:
  • Disconnect the negative battery cable if desired for safety.
  • Remove the engine cover (pulls up off grommets). On some trims, loosening the intake duct for clearance helps.
• Coil removal:
  • Unplug each coil electrical connector.
  • Remove the small coil retaining bolt(s), then twist the coil boot gently to break any seal before lifting straight out.
• Cleanliness:
  • Blow out the plug wells with compressed air so debris doesn’t fall into the cylinders.
• Removal:
  • Use a dedicated spark plug socket and extension. Break free and then back out by hand when loose.
• Installation:
  • Inspect new plugs for damage; verify gap.
  • Thread in by hand first to avoid cross-threading the aluminum head.
  • Torque to 18 lb‑ft (25 Nm). Do not over-tighten.
  • Reinstall coils. A small dab of dielectric grease inside each boot helps sealing and future removal.

Anti‑seize: Modern ACDelco iridium plugs have a nickel-plated shell and are installed dry. GM advises no anti‑seize; it alters torque values and can lead to over-tightening. If you must use it due to environmental corrosion, reduce applied torque by ~20–30%, but the preferred method is clean, dry threads and proper torque.

Misfire diagnosis tip: On DI turbos, a weak plug can mimic injector or coil faults under load. If mileage is high, inspect plugs first and replace as a set.

Known issues

• Ford 3‑valve 2‑piece plug breakage does not apply here.
• The 2.5L LKO does not use a distributor and does not have the historical two‑piece shell failures seen in some other brands.
• GM DI turbo engines are sensitive to plug type. Non‑resistor or incorrect heat range plugs can produce persistent misfire counts and knock sensor activity. Always use the OE iridium spec and verify part numbers by VIN.

Need plugs replaced? Find a shop on Repairius.