Ignition Coil
easy DIY~0.5h jobWritten in plain English and reviewed by the eli5cars editorial team · Last reviewed June 2026
What it does
Your ignition coil is an electrical transformer that takes the 12 volts from your car's battery and boosts it to 30,000–45,000 volts — enough electricity to jump the gap at the tip of the spark plug and create a spark. Modern cars have one coil per cylinder (called coil-on-plug), so if one coil fails, that cylinder stops firing. You lose 1 of your 4 (or 6 or 8) cylinders, and the engine runs rough — like a person trying to sprint on one leg.
Fix-vs-Skip Money Panel
DIY Cost
~$30
parts only
Shop Cost
~$200
parts + labor
Estimates only — real prices vary by region, vehicle, and shop. Updated 2026.
Buy the part
Heads up: some links below are affiliate links (including Amazon Associates) — if you buy through them we may earn a small commission at no extra cost to you. Details: /disclosure.
So what do I do now?
Three honest paths for fixing ignition coil — pick the one that fits your time, tools, and risk tolerance.
Door 1 — DIY it
Parts
- Ignition coil (matched to the misfiring cylinder) ($20–$60)
if one coil failed from age, the others are often close behind — some owners replace the full set at once to avoid repeat labor
Tools
- Socket and ratchet set ($30–$60, one-time)
Consumables
Dielectric grease for the connector/boot
Watch out for
- Match the coil to the cylinder number the misfire code points to (e.g. P0302 = cylinder 2) — don't guess
- A cracked spark plug boot or an oil-fouled plug well can kill a brand-new coil right away — inspect while you're in there
- Unplug the electrical connector gently — the plastic locking tabs on coil connectors are a common breakage point
Skip DIY if: Skip DIY only if the coil is buried under other components (intake, wiring looms) that make removal impractical without a lift — most coil-on-plug engines are genuinely easy here.
Heads up: some links below are affiliate links (including Amazon Associates) — if you buy through them we may earn a small commission at no extra cost to you. Details: /disclosure.
Door 2 — Buy the part
Already have someone lined up to install it (or handy friend), and just need the part?
Search Ignition Coil on AmazonHeads up: some links below are affiliate links (including Amazon Associates) — if you buy through them we may earn a small commission at no extra cost to you. Details: /disclosure.
Door 3 — Go to a shop
Fair price band
$150–$250
parts + labor, typical US pricing
Ask the shop
- Are the parts OEM or aftermarket?
- Is the diagnostic fee waived if I approve the repair?
- Can I get an itemized estimate before you start?
- What warranty do you offer on the labor?
DIY tutorial
Click to load video — helps keep this page fast
Frequently asked questions
How do I know which ignition coil is bad?
The easiest test: swap the suspected coil with one from an adjacent cylinder, then clear the codes and drive. If the misfire code moves to the new cylinder (the one you moved the coil to), the coil is bad. Get a free OBD2 scan first — a P0301 through P0308 code tells you exactly which cylinder is misfiring.
Should I replace all ignition coils at once?
If the car is over 80,000 miles and one coil failed, the others are the same age. Many mechanics recommend replacing all coils while the job is open — coil packs are cheap ($20–$40 each) and the labor is the same whether you replace one or all.
Can a bad ignition coil damage the catalytic converter?
Yes. A coil that fails causes a cylinder misfire, sending raw unburned fuel into the exhaust. That fuel ignites in the hot catalytic converter, overheating and destroying the catalyst. Fix misfires immediately — a $30 coil versus a $2,000 catalytic converter.