A misfire means your engine is not firing on all cylinders, and you should not drive it as a regular car
A misfire is not a problem you can ignore for weeks. Depending on the cause and how severe it is, you might have anywhere from a few miles to a few hundred miles before the engine sustains real damage — but the damage can happen faster than you think, and the cost of repair grows the longer you wait.
The engine control computer detects a misfire when one cylinder fails to ignite its fuel-air mixture on schedule. This throws off the timing and balance of the whole engine. What starts as a rough idle or a noticeable shake at stoplights can become a catalytic converter failure, a cracked engine block, or a seized engine if you keep driving.
The honest answer is: it depends on what is causing the misfire. A fouled spark plug might let you limp 50 miles to a repair shop. A cracked ignition coil might give you 100 miles. A bent valve or a failing fuel injector might fail completely within 10 miles. You cannot know which one you have just by feeling the shake.
Key Takeaways
- A misfire damages your catalytic converter and engine components faster than most drivers realize — often within 100 to 200 miles of continuous driving.
- The longer you drive on a misfire, the more unburned fuel enters the exhaust system and coats the catalytic converter, which can cost $800 to $2,500 to replace.
- Spark plugs, ignition coils, and fuel injectors are the most common causes, and all are cheaper to fix early than to fix after the engine is damaged.
- If the misfire is severe enough to trigger the check engine light, you should drive only to a repair shop, not for daily commuting or long trips.
Why a misfire damages the engine faster than you expect
When a cylinder misfires, the fuel in that cylinder does not burn during the power stroke. That unburned fuel exits into the exhaust system instead. Over time, this fuel coats the inside of your catalytic converter — the part that cleans emissions before they leave the tailpipe. The converter gets clogged and overheats, and eventually it fails.
A catalytic converter failure is not a small repair. Depending on your vehicle, replacement costs between $800 and $2,500. If you catch the misfire and fix it within the first 50 to 100 miles, your converter is usually fine. If you drive 200 miles or more on a misfire, the converter is often already damaged beyond repair.
Beyond the converter, unburned fuel also dilutes your engine oil. The fuel thins the oil and reduces its ability to protect moving parts. If the misfire continues for weeks, the oil breaks down faster, and you risk bearing wear, piston damage, or valve damage — all of which are engine-rebuild territory.
Common causes and how far you can actually drive
The distance you can drive depends entirely on what is broken. Here are the most common causes and what to expect:
| Cause | Typical distance before serious damage | Cost to fix if caught early | Cost if you wait and damage spreads |
|---|---|---|---|
| Fouled or worn spark plug | 50 to 150 miles | $50 to $200 per plug | $800 to $2,500 (converter damage) |
| Failing ignition coil | 75 to 200 miles | $150 to $400 per coil | $800 to $2,500 (converter damage) |
| Clogged fuel injector | 100 to 300 miles | $300 to $900 (cleaning or replacement) | $800 to $2,500 (converter damage) |
| Vacuum leak | 50 to 100 miles | $150 to $400 | $800 to $2,500 (converter damage) |
| Bent valve or broken piston ring | 10 to 50 miles | $1,000 to $3,000 (head work) | $3,000 to $8,000+ (engine rebuild) |
The problem is that you cannot tell which cause you have just by driving the car. A spark plug and an ignition coil both feel similar — a rough idle, hesitation, or a shake. A bent valve feels worse, but you might not know it is bent until the engine seizes.
What to do if your check engine light is on and the engine is misfiring
If the check engine light is on and you feel a misfire, get a diagnostic scan done when ready. Most independent shops and many auto parts stores will scan the code for free or for $50 to $100. The code will tell you whether it is a spark plug, a coil, a fuel injector, or something else.
Once you know the cause, you have a choice: fix it now, or drive carefully to a shop. If the cause is a spark plug or ignition coil, you can usually drive 50 to 100 miles to a repair shop without major risk. If the code points to a bent valve or internal engine damage, do not drive it — call a tow truck.
Do not ignore the light and hope it goes away. The misfire will not fix itself, and the longer you wait, the more damage spreads to parts that cost far more to replace.
How to know if the misfire has already damaged your catalytic converter
If you have been driving on a misfire for more than a few days, your catalytic converter may already be damaged. Signs include a rattling sound from under the car (the converter's internal structure breaking apart), a strong rotten-egg smell from the exhaust, or a sudden loss of power even after the misfire is fixed.
A damaged converter will not show up on a basic diagnostic scan. You need either a visual inspection (a shop looks underneath) or a converter efficiency test (a more expensive scan that measures how well the converter is working). If the converter is damaged, replacement is the only fix — there is no cleaning or repair that restores it.
This is why catching a misfire early matters so much. Fixing a spark plug costs $100. Fixing a spark plug and a converter costs $1,000 or more.
Driving on a misfire: what actually happens to your fuel economy and performance
In the first few miles, you will notice the engine running rough, especially at idle or low speeds. You might feel a shake through the steering wheel or the seat. Acceleration may feel sluggish or hesitant. The check engine light will come on.
As you drive further, the misfire may become worse or stay the same, depending on the cause. A spark plug that is fouled might get slightly worse as it heats up. An ignition coil that is failing might misfire more as the engine warms. A fuel injector that is clogged might stay consistent.
Your fuel economy will drop noticeably — sometimes by 10 to 20 percent — because unburned fuel is wasted fuel. You are paying for gas that never actually powers the engine.
When to tow instead of drive
Tow the car if any of these are true:
- The misfire is so severe that the engine shakes violently or stalls repeatedly.
- The diagnostic code points to a bent valve, broken piston ring, or internal engine damage.
- The car has been misfiring for more than a week and you have not had it scanned yet.
- The misfire started after an accident, impact, or engine overheat.
- You are more than 50 miles from a repair shop and the misfire is getting worse as you drive.
Towing costs $75 to $150 depending on distance, but it is cheaper than a $3,000 engine rebuild. If you are unsure, call a shop and describe what you are feeling. They can usually tell you whether it is safe to drive or whether you need a tow.
Frequently Asked Questions
Can I drive to work with a misfire if it is just one day?
One day of driving on a misfire is unlikely to destroy the engine, but it will damage the catalytic converter. If the misfire is mild, you might get away with one short trip to a repair shop. If it is severe, do not risk it — call for a tow or ask someone to drive you. The repair shop visit is not worth a $1,500 converter replacement.
Will the misfire go away on its own?
No. A misfire is caused by a failed part — a spark plug, ignition coil, fuel injector, or something inside the engine. That part will not repair itself. The longer you wait, the more damage spreads to other parts. The only way to stop a misfire is to fix what is broken.
What if I drive on a misfire for a month?
After a month of regular driving on a misfire, your catalytic converter is almost certainly damaged, your engine oil is diluted with fuel, and you may have additional damage to valves or pistons. Repair costs will likely exceed $2,000 to $4,000. This is why getting a diagnostic scan within the first few days matters so much.
Is a misfire the same as a cylinder not firing at all?
A misfire means a cylinder fails to ignite on one or more combustion cycles, but it may fire on the next cycle. A dead cylinder does not fire at all. Both feel similar when you drive, but a dead cylinder is usually more severe and requires a tow. A diagnostic scan will tell you which one you have.
Can I fix a misfire myself?
If the cause is a spark plug, you can replace it yourself if you have basic tools and know your engine. Spark plugs cost $5 to $15 each. If the cause is an ignition coil, fuel injector, or anything else, you need a shop. Misdiagnosing the problem and replacing the wrong part wastes time and money.