Do cars have ignition coils and spark plugs?

Most gasoline-powered cars do have both ignition coils and spark plugs; diesel cars do not use spark plugs (they use glow plugs and compression ignition), and battery-electric and fuel cell vehicles have neither. The components you’ll find depend on the vehicle’s powertrain: spark-ignition engines rely on coils and plugs to ignite fuel, while compression-ignition and pure-electric systems do not. Below is a breakdown of what these parts do, which vehicles use them, how they’re configured, and what to watch for in maintenance.

What ignition coils and spark plugs do

Ignition coils are transformers that step 12-volt battery power up to tens of thousands of volts. That high voltage jumps the gap at the spark plug tip, igniting the air-fuel mixture in a spark-ignition (gasoline) engine. Coils and plugs work in tandem: the coil generates the spark energy; the plug delivers it precisely inside the combustion chamber at the right moment.

Which vehicles have them — by powertrain

The presence of ignition coils and spark plugs depends on how the vehicle creates combustion or propulsion. The following list explains where you will, and won’t, find them.

• Gasoline (petrol) engines: Yes. They use ignition coils and spark plugs for spark ignition. This includes direct-injection and turbocharged engines.
• Flex-fuel, LPG/CNG, and hydrogen internal-combustion engines: Yes. These spark-ignition variants also use coils and spark plugs, sometimes with higher-energy coils or tighter plug specs.
• Hybrid vehicles (HEV, PHEV, range-extended): Yes, if the hybrid uses a gasoline engine. The engine may run less often, but it still uses coils and spark plugs.
• Diesel engines: No spark plugs. Diesels rely on compression ignition and typically have glow plugs for cold starts. They do not use ignition coils.
• Battery-electric vehicles (BEVs): No. No engine, so no coils or spark plugs.
• Fuel cell electric vehicles (FCEVs): No. The propulsion is electric; there’s no spark-ignition engine.

In short, any spark-ignition internal-combustion engine will have coils and plugs; compression-ignition and purely electric powertrains will not.

How many coils and where they’re located

Modern cars use several coil configurations, which affects how many coils your car has and where they’re mounted. Here are the most common setups you’ll see across model years.

• Single coil with a distributor (older vehicles): One coil feeds all cylinders through a distributor cap and rotor. Common in pre-2000 models.
• Coil pack with “wasted spark”: A shared pack has one coil for every two cylinders, firing paired plugs simultaneously. Common in late-1990s to 2000s.
• Coil-on-plug (COP): One coil per cylinder mounted directly on top of each spark plug. This is the dominant design in modern cars for precise timing and higher energy.
• Coil-near-plug: Individual coils sit close to each plug with short wires. Used where packaging or heat dictates offset mounting.

On most modern engines, you’ll find coils on top of the valve cover(s), each attached to a spark plug that threads into the cylinder head. Engines with two plugs per cylinder (e.g., some HEMI V8s, certain performance or emissions-optimized engines) will have twice as many plugs and often additional coils.

Maintenance, replacement intervals, and symptoms

Typical service intervals

Spark plug life depends on material and duty cycle. Iridium and platinum plugs commonly last 60,000–120,000 miles (96,000–193,000 km); copper plugs may be 20,000–30,000 miles. Hybrids can age plugs by time as much as miles, since short heat cycles and frequent starts are common—follow the automaker’s schedule. Ignition coils aren’t a routine replacement item; they’re usually replaced on failure, though coil boots can harden and crack with age.

Signs of failing plugs or coils

If coils or plugs degrade, drivability and emissions are usually the first clues. Watch for the following issues.

• Misfires or rough idle, especially under load or during acceleration.
• Check Engine Light with codes like P0300 (random misfire) or P0301–P030X (cylinder-specific misfire).
• Hard starting, poor fuel economy, sluggish performance.
• Hesitation, surging, or backfiring under load.
• Oil or coolant in spark plug wells, cracked coil housings, or carbon tracking on plug insulators.

A scan-tool diagnosis is recommended; a “swap test” (moving a suspect coil to another cylinder) can confirm a bad coil if the misfire code follows. Address oil leaks (e.g., valve cover gaskets) that contaminate coils or plugs, and ensure plugs are correctly gapped if your application requires it.

Replacement costs and tips

Costs vary by engine layout and vehicle brand. The points below give typical ranges and best practices.

• Spark plugs: Parts can range from about $5–$25 per plug (copper to iridium). Professional replacement often totals $150–$500 depending on cylinder count and accessibility. Use the OEM-specified plug type and heat range; many modern plugs are pre-gapped.
• Ignition coils: Commonly $50–$200 each for parts; a full set on multi-cylinder engines can run several hundred dollars. Many owners replace only the failed coil; others proactively replace the set on high-mileage engines to avoid repeated labor.
• Installation tips: Use a torque wrench to avoid damaging threads, avoid anti-seize unless the manufacturer specifies it, replace coil boots if brittle, and apply dielectric grease to boots to deter moisture.
• After service: Clear codes, verify no vacuum or intake leaks, and consider checking the PCV system and valve cover gaskets to prevent future fouling.

Sticking with OEM or high-quality equivalent parts helps ensure proper combustion and long-term reliability, especially on turbocharged or direct-injection engines that demand strong, consistent spark.

Edge cases and exceptions

Diesels don’t have spark plugs but do use glow plugs to aid cold starts. Some engines use two spark plugs per cylinder for cleaner combustion or faster flame propagation, increasing the plug count (and sometimes coil count). Rotary engines (e.g., Mazda RX series) use leading and trailing spark plugs and dedicated coils. Specialized ignition systems exist in motorsport and vintage vehicles, but modern passenger cars overwhelmingly use coil-on-plug or coil-near-plug designs.

Summary

Whether a car has ignition coils and spark plugs depends on its powertrain. Gasoline and other spark-ignition engines use both; diesels rely on compression and glow plugs instead; battery-electric and fuel cell vehicles use neither. Most modern cars employ coil-on-plug systems, and while spark plugs are a scheduled wear item, coils are typically replaced only when they fail. Regular maintenance with the correct parts keeps ignition systems performing reliably and efficiently.

How do I know if my ignition coil or spark plug is bad?

You know you likely have a bad ignition coil or spark plug when you see a check engine light, experience engine misfires (rough idling, sputtering), face difficulty starting the car, notice decreased power and fuel economy, or hear backfiring. To determine which part is the issue, you can use a spark tester to check for a strong spark from the coil, or swap spark plugs and coils to see if the misfire moves to a different cylinder. 
This video demonstrates how to identify symptoms of a failing ignition coil or spark plug: 1mFindTheBestCarPriceYouTube · Sep 27, 2023
Signs of a Bad Ignition Coil 

• Blinking or illuminated check engine light
• Engine misfires or rough idling
• Coughing, sputtering, or shaking: engine
• Difficulty starting: or engine stalling
• Reduced power and slower acceleration
• Decreased fuel economy
• Backfiring: from the exhaust
• A strong smell of gas: from the exhaust

Signs of a Bad Spark Plug 

• Engine misfires: and rough idling
• Struggling to start: the car
• Poor acceleration: and sluggishness
• Reduced fuel economy
• Engine knocking or rattling noises

You can watch this video to learn how to check for a bad coil or spark plug: 56sCar and DriverYouTube · May 25, 2012
How to Test for a Bad Coil vs. Bad Spark Plug

1. Scan for codes: Use an OBD2 scanner to get specific codes for misfires on particular cylinders. 
2. Test for spark: With a spark tester, you can observe if the ignition coil produces a strong, blue spark. 
3. Swap components: If you identify a cylinder with a misfire, try swapping the spark plug and ignition coil from that cylinder with parts from a known good cylinder. 
4. Diagnose the issue:
   • If the misfire moves to the other cylinder, the component you swapped was faulty. 
   • If the misfire stays on the original cylinder, the issue might be a bad spark plug, but could also indicate other problems like wiring issues or a faulty fuel injector. 
5. Consult a professional: If you’re unsure, a professional mechanic can perform more detailed tests. 

How much should it cost to replace ignition coils and spark plugs?

The average cost for an Ignition Coil Replacement is between $227 and $335. Labor costs are estimated between $72 and $106 while parts are priced between $155 and $229. This range does not include taxes and fees, and does not factor in your unique location.

Do cars have spark plugs and coils?

Yes, most gasoline-powered cars have both coil packs and spark plugs as part of their ignition system, where the coils generate high voltage to create a spark at the spark plug, igniting the fuel-air mixture and starting the engine. While some modern cars use individual coil-on-plug units, others still use a single “coil pack” with wires or a shared design to deliver the electrical charge to the spark plugs.
 
How they work together

1. Ignition Coils: Opens in new tabThese are transformers that take the low voltage from the car’s battery and amplify it into a high voltage. 
2. Spark Plugs: Opens in new tabThis high-voltage electricity is then sent to the spark plugs, which are located in each cylinder of the engine. 
3. Combustion: Opens in new tabThe spark from the plug jumps across a gap, igniting the fuel and air inside the cylinder, which creates the power needed to run the engine. 

Different configurations

• Coil-on-Plug (COP): Opens in new tabIn many newer cars, a dedicated ignition coil sits directly on top of each spark plug. 
• Distributorless Ignition Systems (DIS): Opens in new tabSome systems may have a single, more complex “coil pack” containing all the coils or multiple coils with individual wires leading to each spark plug. 

Why they’re important

• Engine Performance: A properly functioning ignition system ensures each cylinder fires at the right time, leading to smooth engine operation and good fuel efficiency. 
• Starting: The system is essential for getting the engine to start, as it creates the initial spark needed to ignite the fuel. 
• Misfires: If a coil or spark plug fails, the engine may experience a misfire, which can cause sluggishness, poor performance, and damage to the catalytic converter. 

Are spark plugs and ignition coils the same?

No, spark plugs and ignition coils are not the same; they are distinct, but interdependent components of a vehicle’s ignition system, where the ignition coil transforms the battery’s low voltage into high voltage to power the spark plug, which then ignites the fuel-air mixture in the engine’s combustion chamber. A failure in one can lead to issues in the other, causing engine misfires, poor performance, and a lit check engine light.
 
What is an Ignition Coil?

• An ignition coil is a transformer that steps up the car’s 12-volt battery power to the thousands of volts needed to create a spark. 
• It creates a powerful magnetic field that, when the circuit is broken, generates a high-voltage current. 
• This high-voltage electricity is then sent to the spark plug. 

This video explains how ignition coils work and how they are different from spark plugs: 59sNGK Spark Plugs USAYouTube · Jul 27, 2021
What is a Spark Plug? 

• The spark plug is the component that actually creates the spark.
• It’s designed to fit into the engine’s cylinder head, with its electrode tip positioned to produce a spark that ignites the fuel-air mixture at the correct time.

This video explains the function of a spark plug: 55s1A Auto: Repair Tips & Secrets Only Mechanics KnowYouTube · Sep 10, 2022
How They Work Together

1. The ignition system sends power to the ignition coil. 
2. The coil transforms this into a high-voltage pulse. 
3. This high voltage travels to the spark plug. 
4. The spark plug uses the electricity to generate a spark across its electrodes, which ignites the fuel in the cylinder. 

Symptoms of a Problem 

• Malfunctioning Ignition Coil: Opens in new tabEngine misfiring, reduced power, poor fuel economy, difficulty starting, and a glowing check engine light.
• Malfunctioning Spark Plug: Opens in new tabDifficulty starting, engine misfiring, decreased fuel economy, knocking noises, and the check engine light.

This video demonstrates how to determine if the spark plug or the ignition coil is the problem: 32sWay of the WrenchYouTube · May 19, 2020