If your engine has ever stumbled, hesitated, or suddenly felt like it was running rough for no obvious reason, you may have experienced a misfire. Misfires can feel like a quick jolt, a rough idle, or a loss of power—and while they don’t always mean something catastrophic is happening, they shouldn’t be ignored either.
A misfire happens when one or more cylinders in your engine fail to complete the combustion process correctly. That means the air-fuel mixture isn’t igniting the way it should, and your engine runs unevenly as a result. Here are five common reasons this might be happening and why diagnosing it quickly is important.
1. Ignition System Problems
When people think of misfires, spark plugs are usually the first thing that comes to mind—and for good reason. Worn, fouled, or improperly gapped spark plugs can’t provide a strong, reliable spark, especially under load or during cold starts. Over time, ignition coils can also weaken or fail, causing intermittent or persistent misfires in specific cylinders.
If your vehicle is overdue for a tune-up or you’ve never had the plugs replaced, this is a good place to start. A faulty plug or coil can cause a misfire under acceleration, at idle, or randomly while driving.
2. Fuel Delivery Issues
Your engine needs a precise amount of fuel delivered to each cylinder. When an injector is clogged, a fuel filter is dirty, or a fuel pump isn’t providing enough pressure, one or more cylinders might run too lean. That imbalance can cause a misfire, particularly under heavy throttle.
Sometimes, the symptoms come and go depending on engine temperature or load. If the misfire tends to happen during acceleration or when climbing hills, inconsistent fuel delivery could be the cause.
3. Vacuum Leaks or Air Intake Problems
An engine misfire can also happen when too much air is getting into the system—more than the sensors expect. Cracked vacuum hoses, intake manifold leaks, or a failing gasket can all lead to excess air entering the combustion chamber. This throws off the air-fuel ratio, which causes the engine to run lean and misfire.
A vacuum leak may also be accompanied by a high or fluctuating idle. It’s often more noticeable when the engine is cold and can trigger the check engine light with lean condition or misfire codes.
4. Sensor Failures and Engine Management Errors
Modern engines rely on a range of sensors to manage everything from ignition timing to fuel injection. A failing oxygen sensor, crankshaft position sensor, or mass airflow sensor can confuse the engine control module and cause improper fueling or spark timing.
Sometimes the issue only shows up under specific conditions, which can make it tricky to pin down without a proper diagnostic scan. If you’ve had multiple sensor-related codes or irregular behavior from your vehicle, electrical diagnostics may be needed to track down the root cause.
5. Internal Engine Issues
If the more obvious causes check out and the misfire persists, it might point to mechanical wear inside the engine. Low compression in one or more cylinders, worn valve seats, or sticking lifters can cause a cylinder to misfire, particularly at idle or under light load. These issues tend to appear more often in higher-mileage engines or vehicles that have missed regular maintenance intervals.
While internal problems can be more costly to repair, identifying them early can help prevent further damage. A compression test or leak-down test can determine whether a cylinder is losing pressure and why.
Bexley Automotive – Engine Diagnostics and Repair in Bexley, OH
At Bexley Automotive in Bexley, OH, we will figure out the cause of engine misfires and get their vehicles running smoothly again. Whether it’s a bad coil, a hidden vacuum leak, or something deeper inside the engine, our team can pinpoint the issue and recommend the right repair. If your car isn’t running like it should, let us take a look before a small misfire turns into a bigger problem.