Financing all Credit Types - 
Financing all Credit Types -
Financing all Credit Types -
Financing all Credit Types -
Ignition coils are one of those parts you rarely think about, until your car starts shaking, misfiring, or throwing a check engine light. When an ignition coil fails, the engine doesn’t fire properly, which can quickly snowball into bigger and more expensive problems if ignored.
This guide breaks down what ignition coils do, how to recognize failure early, what misfires really mean, and how codes like P0300 tie directly to ignition coil issues. Whether your car is running rough, losing power, or just turned on the check engine light, this article will help you understand what’s going on and what to do next.
An ignition coil converts your car battery’s low voltage (12 volts) into the thousands of volts needed to create a spark at the spark plug. That spark ignites the air-fuel mixture inside the engine cylinder.
Modern vehicles usually have:
One coil per cylinder (coil-on-plug systems), or
Coil packs that fire multiple cylinders
If even one coil fails, the affected cylinder misfires, meaning it doesn’t fire correctly or at all.
Ignition coil problems rarely appear all at once. Most start subtle and get worse over time.
Typical warning signs include:
Engine misfires or rough idle
Shaking or vibration, especially at stoplights
Loss of power during acceleration
Poor fuel economy
Check engine light (often flashing during severe misfires)
Sulfur or “rotten egg” smell from the exhaust
Car feels fine at idle but stumbles under load
If you’re noticing more than one of these symptoms, ignition coils should be near the top of your checklist.
A misfire happens when a cylinder fails to ignite fuel properly. Ignition coils are one of the most common causes of misfires, along with spark plugs and fuel issues.
When a coil weakens or fails:
Spark becomes inconsistent or disappears
Fuel goes unburned
Engine timing is disrupted
Excess fuel enters the exhaust system
This is where trouble starts, especially for your catalytic converter.
The P0300 trouble code means your engine is experiencing random or multiple misfires, rather than a single-cylinder misfire like P0301–P0308.
Common causes of P0300 include:
Failing ignition coils (multiple or intermittent)
Worn or fouled spark plugs
Coil wiring or connector issues
Vacuum leaks
Fuel delivery problems
Unlike a single-cylinder code, P0300 often points to system-wide ignition weakness, which is why ignition coils are frequently involved.
If P0300 appears alongside rough running, hesitation, or power loss, ignition coil testing should be done immediately.
Yes and this is where delaying repairs becomes expensive.
When an ignition coil fails:
Fuel doesn’t burn inside the cylinder
Unburned fuel enters the catalytic converter
Converter overheats and melts internally
A damaged catalytic converter can cost $1,500–$3,500+, compared to a much cheaper ignition coil replacement.
A flashing check engine light means the misfire is severe enough to cause damage and driving should stop immediately.
Drivers often describe severe misfires as:
Violent shaking during acceleration
Jerking or bucking motion
Engine feels like it’s “dropping cylinders”
Car struggles to climb hills
Sudden loss of power on highways
These are signs the engine is no longer firing evenly, often due to ignition coil failure.
The cost depends on your vehicle and how many coils need replacement.
Average ignition coil replacement costs:
Single ignition coil: $150–$350
Multiple coils: $300–$900+
Labor: $50–$150 (varies by access)
Cost by engine type:
4-cylinder: Lower cost, fewer coils
V6: Moderate cost
V8: Higher cost due to more coils and labor time
Replacing coils early is far cheaper than repairing engine or exhaust damage caused by prolonged misfires.
Technically, yes, but it’s risky.
Short trips may be possible if:
The misfire is mild
The check engine light is not flashing
Performance loss is minimal
However, continued driving increases the risk of:
Catalytic converter failure
Engine damage
Stalling in traffic
If your car shakes heavily or the check engine light flashes, stop driving immediately.
Some vehicles will run for days or weeks with a misfire, but damage accumulates quickly. Even short daily drives can destroy the catalytic converter over time.
Misfires should be treated as urgent, not something to “wait and see.”
Instant Car Fix provides on-site ignition coil diagnostics and replacement, saving you the hassle of towing or sitting in a repair shop.
Our certified mechanics can:
Diagnose misfire causes
Scan and interpret P0300 codes
Test ignition coils and spark plugs
Replace faulty coils quickly
Get your vehicle running smoothly again
Fast diagnosis prevents expensive downstream damage and unnecessary part replacements.
Can a bad ignition coil cause hard starting?
Yes. Weak or failing coils can prevent proper ignition, making the engine struggle to start.
How long do ignition coils last?
Most last 80,000–100,000 miles, but heat, oil leaks, and worn spark plugs can shorten lifespan.
Can ignition coils fail intermittently?
Yes. Heat-related failures often cause misfires only when the engine is warm.
Will replacing spark plugs fix a misfire?
Sometimes, but if the coil is weak, the misfire will return.
Is it better to replace all coils at once?
If multiple coils are failing or mileage is high, replacing them together can prevent repeat breakdowns.
Can bad coils cause poor gas mileage?
Absolutely. Misfires waste fuel and reduce efficiency.
What happens if I ignore a P0300 code?
Continued driving risks catalytic converter damage and engine wear.
Is a flashing check engine light serious?
Yes, it indicates active misfires that can cause immediate damage.