One morning in the workshop, a customer came in and said, “My car doesn’t feel normal anymore. It shakes when I stop, and when I press the gas, it hesitates.” I started the engine myself and immediately felt the uneven vibration. The engine wasn’t running smoothly; it was misfiring.
After 18 years working as an electromechanic, I’ve diagnosed many cases like this. These are typical engine misfire symptoms, and they often appear without warning. The engine may shake, lose power, or feel unstable, but each symptom is a clue.
In this guide, I’ll explain all car misfire symptoms, what causes them, and how to diagnose them step by step, using real diagnostic experience and simple language.
Table of Contents
Engine Misfire Symptoms: The Most Common Warning Signs
Your car is a machine that communicates through feel and sound. When a cylinder isn’t doing its job, it throws the whole engine off balance. Here is exactly what to look for.
Engine shaking or vibration
This is the big one. If you sit in the driver’s seat and feel a persistent shake or tremor through the steering wheel, the seat, or the floorboard, you are feeling an imbalance. Instead of firing smoothly, the engine is physically jolting to one side when a cylinder fails to ignite. It’s most noticeable at a standstill.
Loss of power when accelerating
When you press the gas pedal, you ask the engine for power. If one or more cylinders are misfiring, you simply won’t get it. You might experience a hesitation, a jerking motion, or a feeling that the car is holding back. This is often described as an engine misfire when accelerating, and it happens because the engine is under load and needs full power, but it isn’t there.
Rough idle or unstable RPM
Watch your tachometer (the gauge that shows engine speed). If the needle bounces up and down by 100 or 200 RPMs while you’re stopped, or if the engine feels like it’s chugging, that’s a classic car misfire symptom known as rough idle. The engine is fighting to stay alive because the combustion event in one cylinder is weak or missing entirely.
Check engine light on
In modern cars, the check engine light (CEL) is your best friend. When a misfire is severe enough to damage the catalytic converter (more on that later), the light will often flash at you. This is a “pull over now” warning. If it’s just a steady light, you have a trouble code stored. Either way, engine misfire diagnosis almost always starts with this light.
Engine misfire sound (popping or knocking)
Put down the windows and listen. A misfire often sounds like a popping or sneezing noise coming from the engine bay or exhaust. This is unburned fuel exploding in the hot exhaust manifold. It can also sound like a deep, rhythmic “chugging” sound, distinctly different from the normal smooth hum of a healthy engine.
What Does an Engine Misfire Feel Like and Why It Happens
To understand what an engine misfire feels like, you have to understand the “why.” An engine needs three things to run: Spark, Fuel, and Air (compression). If one is missing in a cylinder, it misfires. Here are the usual suspects.
Spark plug problems
This is the number one culprit. Spark plugs are wear items. Over time, the electrode wears down, or it gets coated in carbon (fouled). A worn spark plug requires higher voltage to fire. When it can’t get that voltage, it fails, causing a misfire. If you’re looking up spark plug misfire symptoms, you’re likely dealing with a simple tune-up issue.
Ignition coil failure
Think of the ignition coil as a tiny lightning generator. It takes your battery’s 12 volts and steps it up to 40,000-60,000 volts to jump the spark plug gap. When a coil starts to fail, it usually happens under load—like when you’re merging onto the highway. It might work fine at idle but break down when stressed, causing an engine misfire when accelerating. Ignition coil misfire symptoms often come on suddenly and get worse quickly.
Fuel injector problems
If the spark is there but the fuel isn’t, you get a misfire. Fuel injectors have tiny nozzles that can clog over time with varnish from bad gas or carbon. If an injector gets stuck closed, no fuel enters the cylinder. If it gets stuck open, it dumps too much fuel, “flooding” the plug so it can’t spark. Both result in a dead cylinder.
Vacuum leaks
Your engine acts like a giant air pump. If unmetered air gets sucked in through a cracked hose or a bad gasket after the mass airflow sensor, it makes the air-fuel mixture too lean (too much air, not enough fuel). A lean mixture is hard to ignite and causes a misfire, especially at idle.
Sensor problems
The Engine Control Unit (ECU) relies on sensors like the Mass Airflow (MAF) sensor, Crankshaft Position sensor, and Oxygen sensors to time the spark and fuel. If a sensor gives bad data, the computer might send a spark at the wrong time or dump the wrong amount of fuel, causing a misfire across multiple cylinders.
How to Diagnose and Fix Engine Misfire (Step-by-Step Guide)
Look, I’m not gonna assume you’re a mechanic. But if you’re the type who likes to get their hands dirty on a Saturday morning, this section is for you. And if you’re not? That’s fine too. Read this anyway, because when you take it to a shop, you’ll know exactly what we’re doing under that hood. Nobody likes getting sold parts they don’t need.
Step 1: Check spark plugs
This is where I start on almost every misfire. Pull the wire or coil off the cylinder that’s acting up—if you have a scanner, you already know which one. Use a spark plug socket to twist it out. Now look at it. I mean really look.
I’ve seen plugs covered in black, dry soot that looks like charcoal. That tells me the engine’s running rich, dumping too much fuel. I’ve pulled plugs that are wet, literally smelling like gas. That usually means fuel’s getting in but the spark’s not lighting it. And I’ve pulled plugs where the gap is worn so wide you could park a truck in it. That’s just age. Here’s the thing: half the time, replacing old worn plugs is the whole damn fix. Don’t overthink it.
Step 2: Check ignition coils
Coils fail in weird ways. Sometimes they work fine at idle then crap out when you hit the gas. Here’s an old trick I still use: wait till dusk, pop the hood with the engine running, and mist a little water from a spray bottle near the coil boots. If you see tiny blue lightning bolts jumping to the engine block, that coil is shot. It’s arcing out instead of sending voltage to the plug.
The pro method? Swap the coil from the misfiring cylinder with a coil from a cylinder that’s running fine. Clear the codes, restart the engine, and see if the misfire moves. If cylinder 3 was misfiring, you swap with cylinder 1, and now cylinder 1 misfires? Congratulations. You found your bad coil.
Step 3: Check fuel injectors
Fuel injectors click. That’s how you know they’re alive. Grab a long screwdriver, put the metal tip on the injector body, and press the handle to your ear. You should hear a steady, rhythmic clicking. Same rhythm as a heartbeat, basically.
If you hear nothing? Dead injector. If you hear a dull thud instead of a clean click? It’s probably stuck partially closed. I had a Dodge Ram last year with a dead cylinder, listened to the injector—nothing. Replaced that one injector and the truck ran smooth as glass. Cost the guy sixty bucks instead of a full tune-up.
Step 4: Check air and vacuum leaks
Engines are just air pumps. If unmetered air gets in after the mass airflow sensor, the computer gets confused and the fuel mixture goes lean. Lean mixtures misfire.
With the engine idling, just listen. Hear a hiss? Follow it. If you can’t hear it, grab a can of carburetor cleaner or brake cleaner. Spray a tiny bit around the intake manifold gaskets and vacuum hose connections. If the engine idle suddenly changes speeds up, slows down, smoothes out you just found your leak. The engine sucked in that spray and used it as fuel. Be careful with this one. Don’t spray near hot manifolds for too long, and don’t use starting fluid. That stuff’s too aggressive.
Step 5: Scan for trouble codes
This is 2025. You need a scanner. They’re cheap. Get one.
Plug it in and read the codes. If you see P0300, that means a random misfire; the computer doesn’t know which cylinder is misfiring, just that it’s happening. But if you see P0301? That’s cylinder one. P0302 is cylinder two, and so on. The last digit tells you exactly where to look. I cannot tell you how many hours this saves. Instead of guessing and throwing parts at it, you walk right to the problem cylinder and start diagnosing. That’s not cheating. That’s working smart.
FAQ – Most Asked Questions About Engine Misfire
What does an engine misfire feel like?
It feels like the car just sneezed. Or stumbled. Sometimes it’s a hard shake like you hit a rumble strip. Other times it’s a hesitation when you step on the gas. You’ll feel it in the seat, the steering wheel, or the floorboards.
What is the most common cause of engine misfire?
Spark plugs. Every time. They wear out. They foul out. They gap out. Ignition coils are second, but plugs are number one by a long shot.
Can I drive with an engine misfire?
You can. But you shouldn’t. A misfire dumps raw fuel into the exhaust. That fuel lights on fire in the catalytic converter and melts it from the inside out. A converter costs $1,000 to $2,500. A tune-up costs $100. Do the math.
Will an engine misfire fix itself?
Never. Not once in eighteen years have I seen one fix itself. It might hide for a minute, but the problem is still there. And it’s getting worse.
Can bad spark plugs cause misfire?
Yes. That’s literally their job. If they can’t spark, the cylinder can’t fire. Replace them on schedule and you’ll avoid most misfires entirely.
How much does it cost to fix engine misfire?
Depends what’s broken. Plugs only? $20 to $100 if you DIY. A coil pack? $50 to $150. A fuel injector? $150 to $400. Burnt valve or blown head gasket? Thousands. The cheaper you catch it, the cheaper it is.
Can low fuel cause an engine misfire?
Indirectly, yes. Run it too low, and the pump sucks up sediment from the bottom of the tank. That clogs injectors. Also, bad gas with water in it will absolutely make a misfire. Water doesn’t burn.
Final Word from an Electromechanic (18 Years Experience)
I’ve said it a thousand times to people standing in my shop: a misfire is your car yelling at you. That shaking, that popping, that hesitation—it’s not normal and it’s not going away. Ignoring it because you’re busy or broke is how a $100 fix turns into a $2,000 nightmare.
I’ve watched guys drive on a flashing check light for “just one more week” and come back needing a whole exhaust system. Don’t be that guy. Diagnose it early. Fix it right. Drive it another 100,000 miles.
You feel something weird? Drop a comment below. Tell me the year, make, model, and what it’s doing. I read every single one and answer what I can. Let’s figure this out together.