What kills an ignition coil?

Coil failures are typically caused by heat and voltage stress, aging, and environmental factors that degrade insulation or windings, leading to weak sparks or no-spark conditions. This article explores the main factors that kill ignition coils and how to reduce the risk.

Electrical stresses that shorten coil life

Primary electrical risk factors

The following electrical conditions commonly stress coils beyond their design limits.

• Overheating from sustained high engine load, limited cooling, or lean/incorrect fuel mixtures that force the coil to work harder.


• Voltage spikes and improper dwell from faulty ignition control modules, worn distributors, or incompatible ignition components.


• Internal winding faults such as shorted or open primary/secondary windings that reduce output or cause failure.


• Moisture, fuel vapor, or conductive contamination entering connectors or the coil housing, which can cause tracking or short circuits.


• Corroded or loose electrical connections and cracked spark plug boots that create arcing or high resistance paths.

Concluding: Electrical stresses—heat, voltage irregularities, and poor connections—are the most common immediate causes of ignition coil failure. Regular inspection of wiring, connectors, and ignition modules helps catch these issues early.

Mechanical and environmental factors

Non-electrical wear and exposure

Coils endure a harsh engine environment, and physical and chemical factors can degrade them over time.

• Thermal cycling: Repeated heating and cooling can crack insulation and reduce dielectric strength.


• Vibration and impact: Road shocks and engine movement can damage windings or crack housings, especially in older or high-mileage vehicles.


• Oil leaks and chemical exposure: Oil, fuel, and cleaning solvents can saturate insulation and erode seals, promoting failure.


• Moisture ingress: Water entry or condensation inside coil assemblies lowers insulation resistance and can cause short paths.


• Age and wear: Insulation materials degrade over time, diminishing coil efficiency and reliability.

Concluding: Mechanical wear, exposure to fluids, and environmental stress accelerate coil deterioration even when electrical inputs are normal. Protecting coils from heat, vibrations, and leaks helps extend life.

Symptoms and prevention strategies

Interpreting signs and taking action

Knowing how coil failure presents itself and how to prevent it can save you from roadside breakdowns.

• Symptoms: engine misfires, rough idle, hard starting, reduced power or acceleration, decreased fuel economy, or a Check Engine Light; in severe cases, a noticeable burning smell may indicate damaged insulation.


• Prevention: maintain the overall ignition system (spark plugs, wires or coils, modules) as a cohesive set; ensure correct ignition timing; protect wiring from heat and moisture; use quality OEM or reputable aftermarket parts; consider replacing coil packs or COPs in sets where recommended by the manufacturer to maintain even performance.

Concluding: Addressing root causes—heat, moisture, and poor electrical connections—alongside regular maintenance reduces coil failures and keeps ignition systems reliable.

Summary

Ignition coils fail mainly due to heat, voltage stress, aging, moisture, oil exposure, and mechanical wear. An integrated maintenance approach—monitoring electrical connections, controlling heat, using quality components, and protecting wiring—helps prolong coil life and prevent unexpected breakdowns.

What to do if your coil is failing

If you notice symptoms of coil trouble, have the system diagnosed with a scan and live data, inspect ignition modules and wiring for corrosion or damage, and replace failing coils or coil packs as recommended by your vehicle’s service guidelines. In many engines, replacing affected coils in pairs or as a complete set maintains balanced performance.

Summary of practical tips

To minimize coil failures, focus on: proper cooling and engine health, clean and secure electrical connections, high-quality ignition components, and protecting the coil area from oil leaks and moisture. Regular maintenance and early diagnosis are your best defense against coil-related ignition problems.

What burns out an ignition coil?

An ignition coil can burn up due to overheating caused by electrical issues like voltage overload, which is often a result of worn spark plugs or faulty wires that increase resistance. Other causes include mechanical damage, age-related insulation breakdown, and environmental factors like excessive heat and moisture. 
Electrical problems 

• Voltage overload: A spark plug with a widened gap requires the coil to generate a higher voltage to create a spark, straining and overheating it. 
• Faulty spark plugs or wires: Worn components force the coil to work harder, creating excess heat. Wires with high resistance can have the same effect. 
• Wiring issues: Faulty or corroded wiring, a poor ground connection, or internal shorts can cause electrical problems and damage the coil. 
• Incorrect voltage supply: If the voltage supplied to the coil is too high, it can cause burnout. 
• Faulty ignition control module: A malfunctioning module can send incorrect signals to the coil, leading to premature failure. 

Mechanical and environmental factors

• Wear and tear: Over time, the internal insulation of the coil can degrade, leading to internal shorts and failure. 
• Vibrations and heat: Constant engine heat and vibrations can physically damage the coil's windings and insulation. 
• Moisture: Moisture can cause corrosion on the coil's terminals and connections, disrupting the electrical path. 

Other causes

• Poor engine tuning: A rich or lean fuel-to-air mixture can put extra strain on the ignition system, including the coil. 
• Improper installation: Incorrect installation can lead to premature failure. 

Why is my engine still misfiring after replacing spark plugs and coils?

Your car may still be misfiring after changing the spark plugs and ignition coils because the problem lies with other components such as the fuel injectors, vacuum leaks, worn spark plug wires, or low engine compression. Other potential causes include issues with the fuel delivery system, airflow to the engine, or ignition timing.
 
This video explains the possible reasons why your car is still misfiring after changing the spark plugs and ignition coils: 59sFixITYouTube · Oct 3, 2024
Other potential causes 

• Fuel system issues: A dirty or malfunctioning fuel injector, a clogged fuel filter, or low fuel pressure can lead to improper fuel delivery. 
• Vacuum leaks: Leaks in the intake manifold or other vacuum lines can cause an imbalance in the air-fuel mixture. 
• Spark plug wires: Even with new coils, old or damaged wires can prevent a strong spark from reaching the plugs. 
• Low compression: This can be caused by issues like a worn piston ring, a leaky valve, or a blown head gasket, all of which prevent the cylinder from compressing the air-fuel mixture effectively. 
• Incorrect timing: If the ignition timing is off, the spark plug won't fire at the right moment for efficient combustion. 
• Faulty new parts: It's possible that one of the "new" parts is defective, so it's worth swapping the new coil with one from a cylinder that isn't misfiring to see if the problem follows the coil. 
• Wiring and connector issues: Corroded, damaged, or loose connectors to the coils or fuel injectors can cause misfires. 
• Carbon buildup: Excessive carbon deposits on the intake valves can prevent them from sealing properly, especially in direct-injection engines. 

Why does my car keep killing the ignition coils?

Ignition coils overheating and shorting can result from faulty spark plugs, wiring shorts, or a failing ignition control module. Inspect spark plugs for wear or incorrect gap, check coil wiring harness for damage or corrosion, and test the ignition control module for proper function.

What can cause an ignition coil to fail?

Ignition coils can fail due to excessive heat, vibration, moisture, or electrical issues like worn-out spark plugs and voltage surges. Other common causes include fluid leaks, improper installation, general wear and tear over time, and faults in the vehicle's electrical system, such as a weak battery or faulty wiring. 
Environmental and operational causes

• Excessive heat and vibration: The engine's harsh environment can degrade insulation and cause cracks in the coil over time. 
• Moisture: Water intrusion from heavy rain, washing the engine bay, or cracked seals can cause corrosion and failure. 
• Fluid leaks: Oil or coolant leaks can contaminate the coil, causing damage and reducing its efficiency. 
• Wear and tear: Age and mileage cause the coil's components to degrade naturally. 

Electrical and component-related causes

• Worn-out or faulty spark plugs: A bad spark plug with a worn or incorrect gap forces the coil to work harder, leading to overheating and premature failure. 
• Electrical overload: A faulty alternator or voltage regulator can send excess current to the coils, shortening their lifespan. 
• Electrical system faults: Issues like a weak battery, corroded connectors, or a damaged wiring harness can disrupt the electrical supply. 
• Improper installation: Using the wrong type of coil or installing it incorrectly can lead to premature failure.