2019 GMC Sierra 1500 — Spark Plug Type, Gap & Torque

Quick reference

Note: GM used multiple VIN/RPO-specific ACDelco plug part numbers in 2019. Always confirm the exact PN on the underhood emissions label, owner’s manual, or by VIN at a dealer/parts catalog. Motorcraft is Ford’s OE brand and generally not applicable to GMC.

Why the right plug matters

• Heat range: Modern GM engines are sensitive to plug heat range. Too hot can cause pre-ignition and electrode wear; too cold can foul and misfire. Matching the OE heat range for your exact RPO (L3B, LV3, L82/L84, L87) is critical.
• Electrode metal:
  • Iridium: Factory spec on 2019 Sierra 1500 engines. Fine-wire iridium offers strong spark with less voltage, superior durability, and 100k‑mile service life.
  • Platinum: Acceptable on some older platforms, but not ideal here—shorter life and potential for roughness on direct-injected engines.
  • Copper/nickel: Great conductivity but short life (often 30k miles). Not recommended for these engines.
• Design details: Projected tip length and resistor values affect ECM misfire detection and cylinder pressure readings. Stick with OE-equivalent iridium plugs from ACDelco or high-quality equivalents from NGK/Denso that match the OE design.

How to gap a spark plug

Most iridium plugs arrive pre-gapped to specification, but verify before install:

1. Measure with a wire-style gap gauge (not a coin/pry type). Target the spec in the table for your engine; confirm on the underhood label.
2. Adjust only the ground strap if needed—very lightly. Do not touch or pry against the fine-wire iridium center electrode.
3. Re-check in multiple spots around the gap to ensure the ground strap is parallel to the center electrode.
4. If a plug was dropped or the porcelain is chipped, discard it.

Replacement procedure tips (2019 Sierra 1500)

All 2019 Sierra 1500 engines use coil-on-plug ignition—no distributor or plug wires.

• Access: Remove the engine cover. Work one cylinder at a time to avoid cross-connecting.
• Coil removal: Unplug the coil connector, remove the coil hold-down bolt, then twist the coil boot to break it free and pull straight up.
• Clean: Blow out the plug well with compressed air before removing the plug so debris doesn’t fall into the cylinder.
• Removal: Use the correct spark plug socket (magnetic or rubber insert) with an extension. Break loose on a cool engine only.
• Inspect: Check boots for carbon tracking or tearing; replace any damaged boots.
• Install: Start the new plug by hand at least 5–6 turns to prevent cross-threading. Torque to 15 lb-ft (20 Nm) unless your service info specifies otherwise for your exact plug/seating style.
• Anti-seize: GM/ACDelco nickel-plated plugs are designed to be installed dry. Anti-seize is not recommended and will alter torque values if used.
• Dielectric grease: A thin film inside each boot helps sealing and future removal. Do not pack the terminal.
• Final check: Reconnect coils, clear any stored misfire codes, and verify smooth idle under load.

Known issues and notes

• VIN/RPO-specific plugs: The 2019 lineup (L3B, LV3, L82/L84, L87) uses different OE part numbers and sometimes different gaps. Using the wrong heat range or design can trigger misfire counts, rough idle, or reduced fuel economy—verify by VIN.
• Stuck plugs in aluminum heads: Long service intervals can let plugs seize. Always remove on a cold engine. If resistance is high, crack loose 1/8 turn, soak the threads with penetrant, and work the plug back-and-forth to protect the threads.
• Coil boots: Boots can stick to the porcelain and tear. If a boot is oil-soaked or carbon-tracked, replace it; misfires often track along boot damage rather than the plug itself.
• Direct injection sensitivity: Short-trip driving can promote deposits. Fresh OE-spec iridium plugs plus periodic highway runs help keep tips clean. If misfires persist, consider intake/valve deposit inspection.

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