How to How to Replace Spark Plugs
Worn spark plugs cause poor fuel economy, rough idle, and hard starting. Replace spark plugs every 30K-100K miles depending on type to maintain engine performance.
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0 of 7 steps completedStep-by-Step Instructions
1 Step 1: Determine Replacement Interval
Mike Johnson: "Pro tip: Make sure to double-check this before moving to the next step..."
Step 1: Determine Replacement Interval
Check owner's manual for interval: standard copper plugs every 30K miles, platinum every 60K, iridium every 100K miles. Signs you need replacement: rough idle, poor acceleration, decreased MPG, hard starting.
2 Step 2: Purchase Correct Spark Plugs
Mike Johnson: "Pro tip: Make sure to double-check this before moving to the next step..."
Step 2: Purchase Correct Spark Plugs
Buy exact type specified in manual - wrong plugs cause major problems. Note: gap size, heat range, thread size. Most cars use 4-8 plugs. Iridium costs more but lasts longer - worth it.
NGK Iridium Spark Plugs (set of 4)
Premium plugs, 100K mile life, better performance
3 Step 3: Access Spark Plugs
Mike Johnson: "Pro tip: Make sure to double-check this before moving to the next step..."
Step 3: Access Spark Plugs
Engine must be cool. Locate plugs - they're attached to thick wires or coil packs on top of engine. May need to remove engine cover, air intake, or other components. Take photo before disconnecting anything.
4 Step 4: Remove One Plug at a Time
Step 4: Remove One Plug at a Time
IMPORTANT: Only remove/replace one plug at a time to avoid mixing up firing order. For coil-on-plug: unbolt coil, pull straight up. For plug wires: twist boot, pull firmly. Use compressed air to clean area around plug.
5 Step 5: Remove and Inspect Old Plug
Step 5: Remove and Inspect Old Plug
Use spark plug socket and ratchet. Loosen carefully - if stuck, apply penetrating oil and wait. Inspect old plug: tan/gray = good, black/sooty = too rich, white = too lean, oil on threads = valve cover leak.
6 Step 6: Gap and Install New Plug
Step 6: Gap and Install New Plug
Check gap with gauge (should match spec, usually 0.028-0.060"). Adjust if needed by bending ground electrode. Apply tiny amount of anti-seize to threads (not pre-coated plugs). Hand-thread plug - MUST go in straight. Tighten to spec (usually 1/4 turn after snug).
7 Step 7: Reconnect and Test
Step 7: Reconnect and Test
Reinstall coil or plug wire. Repeat for remaining plugs one at a time. Reconnect any removed components. Start engine - should idle smoothly. Test drive to verify improved performance.