Engine
What is an Ignition Coil?
Turns 12 volts into 30,000+ volts to light the spark plug.
Simplified animation — not to scale.
In plain English
A small transformer (sometimes one per cylinder) sitting on top of the spark plug. It takes battery voltage and steps it up massively.
A simple analogy
"It is a tiny lightning generator — turns a polite 12-volt nudge into the bolt that lights the fire."
How it works
The ECU triggers the coil, which dumps a huge high-voltage pulse into the spark plug at exactly the right moment to ignite the fuel-air mixture.
Signs of trouble
- ⚠Misfires, especially under load
- ⚠Juddering or shaking
- ⚠Loss of power and bad MPG
- ⚠Check engine light with misfire codes
Rough UK cost
£70–£300 per coil (petrol only)
Parts: £25–£100 per coil
Labour: £40–£150
Always get a written quote. Prices vary by car, region, and parts brand.
Heads up: Carautonomy is for general guidance only. If your car is showing warning lights or behaving oddly, get it looked at by a qualified mechanic.