Ignition coils transform 12V battery power into the 20,000-50,000V needed to fire spark plugs.
A primary winding charges and collapses, inducing a high-voltage pulse in the secondary winding. Coil-on-plug designs use one coil per cylinder.
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Replacement runs $80–$600 including parts and 0.3-2 hours labor. Exact cost depends on vehicle, parts tier (OEM vs aftermarket), and local labor rate.
Expected lifespan is 80,000-120,000 miles. Driving conditions, climate, and maintenance affect real-world life.
Misfires on one cylinder; Stumble under load; Check-engine light; Hard starts in damp weather; Bad fuel economy.
Most modern ignition coilss are sealed units that get replaced rather than rebuilt. A shop will diagnose, confirm with a load or output test, then swap the unit and verify operation.
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