A misfire can start out feeling like a tiny hiccup, then suddenly the check engine light starts blinking, and your confidence drops fast. The car may shake at idle, hesitate when you merge, or feel like it lost a chunk of power for no clear reason. At that moment, most drivers have the same question: Is this a simple tune-up issue, or something more complicated hiding behind it?
The clues are usually there, you just have to know what to pay attention to before the problem gets worse.
What A Misfire Feels Like In Real Driving
Misfires do not always feel dramatic. Sometimes it is a subtle stumble when you accelerate, especially uphill or when the engine is under load. Other times, the engine shakes at a stoplight, then smooths out once you are cruising. You might also notice the exhaust sounds uneven, or the car feels like it is working harder to do normal things.
Pay attention to consistency. A steady rough idle that never goes away can point toward a persistent ignition issue. A misfire that comes and goes, especially in damp weather or after the engine warms up, can hint at a coil or electrical problem that is sensitive to heat and moisture.
Why A Blinking Check Engine Light Changes The Urgency
A solid check engine light can mean a lot of things, some minor, some not. A blinking light is different. In many vehicles, a blinking light means the engine is misfiring severely enough that unburned fuel may be entering the exhaust system. That extra fuel can overheat and damage the catalytic converter, which is one of the more expensive parts on the car.
This is not a panic situation, but it is a stop-putting-it-off situation. If the light is blinking and the engine is shaking, it is smart to drive gently, avoid hard acceleration, and get it inspected soon. The longer it misfires, the more secondary damage it can cause.
How Worn Spark Plugs Typically Cause Misfires
Spark plugs wear slowly, so the symptoms often creep in. As the gap increases and the tip wears, the spark becomes weaker, especially under load. That is why a worn plug problem may show up first when you accelerate onto the freeway, climb a hill, or run the A/C on a hot day.
Worn plugs can also cause a rough idle, but the bigger giveaway is a gradual decline. Fuel economy may drop a bit, the engine may feel less smooth than it used to, and starting may take an extra second. If plugs are overdue, that alone can be enough to trigger misfires, and it can also stress ignition coils by making them work harder to jump a wider gap.
How Ignition Coils Fail And What Makes Them Act Random
Coils tend to fail in a less predictable way. A coil can work fine when cold, then break down when it heats up. It can also misfire more in damp conditions or when the engine bay is under higher electrical load. That is why coil-related misfires often feel random at first.
A failing coil may cause a sharp stumble that comes on suddenly, then disappears for a while. Some drivers describe it as the engine dropping a cylinder for a moment, then catching again. In more advanced cases, the misfire becomes constant, and the blinking light shows up more often because the cylinder is not firing reliably.
Misfire Patterns That Help You Tell Plugs From Coils
You cannot diagnose this perfectly from the driver’s seat, but patterns can point you in the right direction. Here are the behaviors we listen for when a customer explains what they are feeling:
- Misfire gets worse under load, like hills or acceleration, and the plugs are overdue, spark plugs move higher on the suspect list.
- Misfire is intermittent and seems tied to heat soak, like it starts after a short stop, ignition coils become more likely.
- Misfire shows up more in wet weather or after a car wash, coil boots, and coil insulation are worth checking.
- Misfire is isolated to one cylinder and stays there when tested, a single coil or plug is often the culprit.
- Misfire moves to a different cylinder after parts are swapped during testing, which strongly points to the swapped part.
We see this a lot: plugs wear gradually, coils often fail in a more on-off pattern, and both can overlap if the system has been strained for a while.
What To Do If The Light Is Blinking And The Engine Is Shaking
First, avoid pushing the engine. Keep acceleration gentle, skip towing, and do not test it by flooring it to see if it clears up. If the car is shaking badly or the power is very limited, it may be safer to shut it down and arrange a tow rather than risk overheating the exhaust system.
Do not start replacing parts at random, either. A proper diagnosis checks codes, reviews misfire counts, verifies spark and fuel behavior, and inspects the plugs and coils for obvious issues such as oil in the plug wells or damaged boots. We’ve seen plenty of cases where the root cause was a simple maintenance item, and just as many where a misfire was caused by something like a vacuum leak or fuel delivery problem that looked like ignition at first.
Get Misfire Diagnostics in Martinez, CA with Hagin's Automotive
We can pinpoint which cylinder is misfiring, test whether spark plugs or ignition coils are at fault, and confirm there is not another issue causing the same symptoms. We’ll explain what we find clearly and recommend the repair that makes the most sense, so you are not replacing parts blindly.
Call Hagin's Automotive in Martinez, CA, to schedule a misfire and blinking check engine light inspection and get your car running smoothly again.