For the car engine to work properly, the perfect mixture of air and fuel is required, along with a clear and strong spark. If any of these things fail, it will not ignite the combustion chamber properly and a misfire will occur.
If your car engine is misfiring, it is important to find out the cause and fix it as soon as possible. Misfires can cause all sorts of problems, from reduced fuel efficiency to complete engine failure. But how do you tell if your engine is misfiring, and what could be causing it?
In today’s article, we will discuss the meaning of engine misfires and what possible issues can cause them. We’ll also look at how to determine if your engine is misfiring and answer some common questions about misfires.
What is an Engine Misfire?
An engine misfire is an event that occurs when one or more of the engine’s cylinders fail to ignite the air/fuel mixture during the combustion cycle. This can lead to a variety of engine performance issues and can even lead to serious engine damage if left untreated.
For complete cylinder combustion to occur, the engine needs three important things, and that is the correct air/fuel mixture, compression, and spark. If any of these are missing or incorrect, the cylinder combustion will not be done correctly, and no power will be created.
The engine control module monitors the crankshaft rotation speed with the crankshaft position sensor, and if the speed does not increase slightly on a cylinder after the combustion, it means that the engine is misfiring, and a trouble code will be stored.
The most common code you will see is the P0300 code, along with a code like P030X. The X is replaced with the cylinder number where the cylinder misfire occurs; for example P0301 is a cylinder 1 misfire.
What Are The Causes Of An Engine Misfire?
The most common causes of engine misfires are bad ignition coils or failed spark plugs. It can also be caused by fuel-related issues such as a faulty fuel injector or a bad fuel pump. In rare cases, it can also happen because of low engine compression.
Here is a more detailed list of the most common cause of engine misfires:
1. Bad Ignition Coil
The most common cause of an engine misfire is a bad or failing ignition coil. Some vehicles have a separate ignition coil on every spark plug, while some cars have one coil pack with an ignition wire to each spark plug.
Older cars use a distributor to distribute the spark to all the spark plugs, which are powered by an ignition coil. If either the distributor or the ignition coil creates a weak spark, it can cause misfires.
READ MORE: 6 Symptoms of a Bad Ignition Coil (& Replacement Cost)
2. Failed Spark Plug
The second most common cause of a misfiring engine is bad or failing spark plugs. The function of the spark plug is to ignite the air-fuel mixture in the combustion chamber, and if there is something wrong with the spark plug, it will not ignite, and a misfire will occur.
Spark plugs should be replaced on a schedule for all car models, and not replacing them on time can cause fouled spark plugs, which can cause misfires. If you don’t know when you last changed the spark plugs, you need to check your service manual and replace them if necessary.
Read more: How Long Do Spark Plugs Last?
3. Intake Manifold Gasket Leaks
There is a gasket located between the cylinder head and the intake manifold called the intake manifold gasket. If this gasket leaks, it will draw air into the combustion chamber, causing the air-fuel mixture to become too lean, and this can cause misfires.
There are also many vacuum lines on the intake manifold that can leak, giving the same symptoms as a bad intake manifold gasket. However, finding these vacuum leaks is often quite easy and we will talk about that further down in the article.
RELATED: 5 Signs of a Bad Intake Manifold Gasket (& Replacement Cost)
4. Low Fuel Pressure
Low fuel pressure is another thing that can cause misfires. Low fuel pressure causes less fuel to enter the engine’s combustion chambers, resulting in a lean air-fuel mixture that can cause misfires on all cylinders. Low fuel pressure can be caused by a faulty fuel pressure regulator, a faulty fuel pump, or a clogged fuel filter.
Fortunately, checking the fuel pressure in your car is fairly easy with a manual fuel pressure gauge, and worth doing if you suspect low fuel pressure.
Read more: Low Fuel Pressure – Symptoms, Causes (& How To Fix it)
5. Faulty Injector
The fuel injectors supply the combustion chamber with the correct amount of fuel for each cylinder, and there is usually a separate fuel injector for each cylinder. If the fuel injector injects the wrong amount of fuel, it will cause the engine to run rich or lean, which can lead to engine misfires.
Failed injectors aren’t very common on most modern car models, and because of this, you’ll want to check out the other possible causes first. If you can’t find the issue elsewhere, it’s definitely worth taking a look at your fuel injectors.
Read more: 8 Symptoms of a Bad Fuel Injector (& Replacement Cost)
6. Bad Engine Sensor
The engine in modern cars uses many sensors to measure everything in the engine to make them as efficient as possible. Failure of any of these sensors can cause an incorrect air-fuel mixture to enter the engine, which can cause the engine to misfire.
The most common car sensors that cause an incorrect air-fuel mixture are the MAF sensor, the MAP sensor, the oxygen sensor, and the coolant temperature sensor.
READ MORE: 15 Types of Car Sensors (& What They Do)
7. Low Compression
As we talked about earlier, the engine needs the right air-fuel mixture, spark, and compression to fire properly. If you already checked the fuel supply and the spark and couldn’t find any problems with it, there is a risk of low compression in your engine.
To find out if your engine has low compression, you need to do a compression test and compare the results to the manufacturer’s specifications. Unfortunately, low compression problems are often caused by worn parts inside the engine, which can be very expensive to fix, so you’ll want to inspect the other possible causes first.
RELATED: 8 Causes of Low Compression in a Car Engine (& How to Fix)
What Are The Symptoms Of Engine Misfires?
The main symptoms of an engine misfire include:
- Rough Acceleration
- Rough Idle
- Vibrations
- Check Engine Light
- Engine Sound Changed
Here is a more detailed list of the most common signs of engine misfires:
1. Rough Acceleration
When an engine misfire occurs, you may feel a strong or light jerk coming from the engine. These misfires often occur under load from the engine, such as when you accelerate quickly.
The most common situation where you will feel misfires is in high gear, low RPM, and with the gas pedal to the floor. Rough acceleration is a typical sign that your engine is misfiring.
You may also notice other performance issues, like slower acceleration than usual or a stalling engine while accelerating.
2. Rough Idle
The car engine is most sensitive to small air-fuel mixture problems at idle, so this is probably one of the first places you will notice misfires.
Therefore, if you notice that your car engine idles rougher than usual, it could be a sign of a misfiring engine. You may also notice problems such as the engine stalling at idle or an uneven idle that jumps up and down.
3. Vibrations
A car engine is very balanced when it is manufactured and often has balance shafts and various tricks to get as little vibration out of it as possible.
When one or more cylinders do not fire properly, the engine will become unbalanced, and this can cause severe vibrations inside your car when accelerating or idling. You can also open the hood of your car and watch the engine idle. If you notice that it vibrates more than usual, it could be a sign that the engine is misfiring.
4. Check Engine Light
Modern cars have good monitoring systems for all the different car sensors on the engine. If a sensor is failing or a sensor detects that something is wrong with the engine, it sends the information to the engine control module.
When the engine control module receives the data, it will determine if the problem is serious or not. If the problem occurs repeatedly, the engine control module will illuminate the check engine light to let you know that something is wrong so that you can have it repaired.
If you see a blinking or flashing check engine light, that’s another strong sign that your engine is misfiring.
5. Engine Sound Changed
If you know a little about cars, you’ve probably noticed a difference in sounds from different engines. V8 engines have a completely different tone than a four-cylinder engine, for example.
Therefore, if your 4-cylinder engine misfires on one cylinder, it will sound like a 3-cylinder engine. If your car engine sounds unusual, it’s possible that your engine is misfiring on every cycle.
How To Fix Engine Misfires?
To fix engine misfires, you need to read the trouble codes from the engine control module and continue troubleshooting from there. You’ll also want to inspect the spark plugs and ignition coils. Then, you want to look for vacuum leaks and cylinder compression.
Here is a more detailed list of how to diagnose and fix engine misfires:
1. Check Trouble Codes
Modern car engines have a system that monitors all the sensors in the car engine, and if there is something wrong with a sensor, it will store it as a trouble code in the engine control module.
Therefore, the first thing you want to do when diagnosing misfires is to check the trouble codes with an OBD2 scanner. You can either get one yourself, or go to a mechanic and borrow their diagnostic tool to read the trouble codes from the ECM.
This will give you important information. For example, if you see a trouble code like P0300 or P030X, it means that the ECM is detecting a misfire on a specific cylinder, and you may want to start checking the spark plug or ignition coil on that cylinder.
If you find trouble codes on an engine sensor or low fuel pressure, you’ll want to start the diagnosis from there. It is important to start by reading the error codes to know where to start troubleshooting.
2. Check Spark Plugs and Coils
If you have a misfire trouble code on a specific cylinder, you’ll want to start by looking at the spark plugs and ignition coil on that cylinder. Remove the spark plug and ignition coil from that cylinder and visually inspect them and replace them if they look bad or dirty.
An old trick that mechanics often use on car engines with separate ignition coils is to switch the spark plug and ignition coil to another cylinder. Then, clear the codes and drive for a while to see if the problem has moved to another cylinder. If it did, you know it’s a problem with either the spark plugs or the ignition coil, and you will want to replace all the spark plugs and the ignition coil on that cylinder.
3. Check vacuum leaks
If you can’t find any problems on the spark side, it’s time to look at the air-fuel mixture. Vacuum leaks are a common cause of an incorrect air-fuel mixture and are fairly easy to check, so you want to start there.
You can check for vacuum leaks by gently spraying a flammable spray around the engine’s intake manifold while the engine is idling. If the engine speed increases, it means there is a leak and the engine is injecting the flammable spray. However, be very careful when doing this and have a fire extinguisher ready.
You can also use an EVAP smoke machine to easily find vacuum leaks, but these are often quite expensive and probably not something most people have in their garages.
Learn more here: How to find a Vacuum Leak & How to Fix It (8 Easy Steps)
4. Check fuel pressure
The next thing you want to check is the fuel pressure. Although most modern cars use an electric fuel pressure sensor, you’ll want to confirm the results with a manual fuel pressure gauge, because an electronic sensor can fail.
Connect a fuel pressure gauge to the fuel rail and start the engine. Check the fuel pressure and compare it to the manufacturer’s specifications. If it is too high or too low, you need to inspect the components of the fuel system such as the fuel pump, fuel filter, and fuel pressure regulator.
5. Check Compression
You also want to ensure that the engine’s compression is correct, so you must do a compression test on all cylinders. You can do this with either a compression tester or a leak-down tester.
Compare the results with the manufacturer’s specifications, and if the compression is low on a cylinder, you need to inspect the engine parts such as the timing belt, piston rings, valves, or pistons. All of these parts are often very expensive to replace, so you want to make sure you do a proper diagnosis before replacing them.
6. Take it to a mechanic
If you’ve checked all the things above, but still can’t figure out what’s causing the misfires in your engine, it might be worth taking the car to a professional mechanic instead. Engine misfires can actually be quite difficult to diagnose even for us experts in the field.
Even if you think it will be very expensive to take the car to a mechanic, it can actually sometimes be cheaper to get a proper diagnosis rather than replacing fully functional parts.
Is Engine Misfire Serious?
Yes. Engine misfires are serious. When an engine misfires, it can cause reduced fuel economy, engine damage, and a loss of power. In some cases, it can also lead to dangerous situations where the car stalls and becomes difficult to steer due to the loss of power steering. It can also seriously damage your engine.
What Does An Engine Misfire Feel Like?
If your engine misfires, it will feel like the engine is shaking or vibrating, and it may make a knocking noise. You may also notice that the engine does not sound like it used to, and that your car has reduced power and fuel efficiency. If you think you may have a problem with engine misfires, the best thing to do is take it to a mechanic to have it checked out.
How Much Does It Cost to Fix Engine Misfires?
You can expect a cost of $200 to $500 to fix a misfiring engine in most cases. However, it depends on how serious the fault is and what specific repairs need to be made. Some of the most common causes of engine misfires are bad spark plugs or a bad ignition coil, which can be relatively cheap to repair. If you’re unlucky, it could be due to poor compression, which can be very expensive to repair.
How long can you drive with a misfiring engine?
It is not recommended to drive your car at all with a misfiring car engine. If you suspect that your engine is misfiring, it is important to take care of the problem as soon as possible. Continuing to drive with a misfiring engine can cause serious damage to your car’s engine.
Can I drive with a misfiring engine?
No. It’s not recommended to drive with engine misfires. Misfires can cause serious damage to your engine’s internal parts and the catalytic converter, which can be very costly to repair. It’s best to diagnose and repair the issue as soon as possible.
Conclusion
A misfiring engine can be a serious problem that should be fixed as soon as possible. By understanding the causes, symptoms, and how to fix it, you can keep your car running smoothly and avoid expensive repair costs.
Fixing a misfiring engine can sometimes be difficult without the right knowledge and tools, due to the multitude of possible causes. Therefore, if you have checked the basics, it may be worth taking your car to a qualified mechanic for expert advice.
I hope you enjoyed this article and now have the expertise to diagnose engine problems like misfires and fix the problem with your car yourself to save some money.
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33 thoughts on "Engine Misfire – Meaning, Causes, Symptoms & How To Fix It"
antero villarreal jr.
i have a 2013 kia forte, the check engine light came on and, the car does not have an engine problem. My problem is, that it starts shaking when I accelerate to a certain speed. When it reaches normal speed it quit shaking. Could it be a cv joint problem? I have not noticed any slack in the joint. Puzzled.
Magnus Sellén
If the check engine light is on, there should be a trouble code stored that needs to be checked with an OBD2 scanner. So I would start there and then continue troubleshooting from whatever code you get. If the problem comes from the drivetrain and not the engine, the CV joints or driveshafts are common causes.
Gareth
I have a golf 6 TSI model 2010, I changed new spark plugs, ignition coil and spark plugs cables but the car still misfires at times but not always.
Mark
97 Toyota 4Runner 2.7 engine. 165k miles #1 cyl misfire code. runs rough, no white smoke, no water in oil. Verified plugs and wires by swapping #1 with #3. Still #1 misfire. Getting good spark. Removed all wires one at time, #2,3,4 all made engine want to stall when removed. Removing #1 resulted in NO difference in idle. Did compression test and cylinders were 150, 150, 149, 149. Spark plugs were normal, except #1 as it was slightly oily/wet after cleaning with wire brush and reinstalling and restarting for about 10 minutes. The injectors are installed Under valve cover and to get to them the plenum and intake manifold needs to be removed. Not sure how to test injectors. Any advice is welcomed. Thx
john
My toyota vitz 2nz engine still misfiring even after puting new plugs wat can b the problem
Cody
I have a 2003 BMW 745i 7 series. I’m not sure what’s going on but whenever I try to drive it I’ll put it in drive and it will start to go and when you give it gas it will accelerate for a second then rev high like it shifted into neutral then shift and it will repeat that same cycle until the car switches into failsafe mode.. any advice on where to start?
Damiete Bob-manuel
My Toyota corolla 2009 cylinder 2 & 3 is misfiring. In fact, nuzzle 2 & 3 does not bring up any sign it is OK when removed from the plug head to the nuzzle. Hearing some funny sound underneath the engine. Check light blinking, car acceleration slow. Rev going down and vibrating when gear is engaged. What do I do?
Zain
Hi guys Zain here My caddy 1.6 carb had still misfired after changing coil, boggy cords, plugs, distributor cap, rotor and some fuel lines. I finally adjusted the float screw anti clock wise and my problem was solved. Regards Zain
Mike
I have a 2014 chrysler town and country van 3.6 engine number 3 cylinder misfire changed coils, spark plugs ,fuel injectors compression 130 # wires good to and from injectors good,ohlms across injectors,air filter good, intake gasket good added heat to gas tank. What else can I do???
tracy leutz
I have a 2012 ford focus we just put a new ,used engine in it when I got it back the ck engine light was on we replaced the o2 sensor,then came the cylinder 1 misfire,changed out spark plug and coil still has the same code ???
hari babu
i have hyundai accent 2012 model ,manual gear.my car RPM fluctuates even after i changed my coils ( 3 coils are good and one coil current was leaking so i changed only that coil),plug ,air filter etc.kindly suggest what is the remedy for this problem.
Thomas
Hello from Denmark .I have a Audi A6 C4 2.8 ACK engine ,somtime i lose Ignition on one cylinde,i have change the spark plugs,ignition coil and the spark plugs wires.when i pull the spark plugs wires out from the spark plug next to the one that dont work it comes back one ..and all 6 cylindre works fine .then i can take the car for a spin and the same thing happen...to i pull out the spark plugs wires next to the bad one ..and its on the same cylinder every time ..is it a bad injection valve ? or my ECU ? Best regards,
Zain
Hi Mr. Sellèn I would like to congratulate you on the simple way of explaining this article on misfire troubleshooting. I've been on other websites trying to find more info on what to do on my VW caddy 1988 model which I'm experiencing misfiring. I thank you for making my life so much easier I'm going forward finding my problem. I will definetly come back for more updates on how to solve car problems. Best regards, Zain from S.A
Sanjay
I have a bmw e30 320i 1989. The car wont rev up over 3000revs per min.could iit b a bad ignition coil. I hav tried out diff tps sensor,air flow meter,changed plugs an plug leads an checked the distributor.fuel pressure 7bar on idle.pls cn you assist
senyanja julius
what could be the cause of car engine running and stopping on the road?
Keith Devine
My 2004 skoda octavia 1800 petrol turbo 20 valve engine is misfiring ive had it on dinostic and nothing is showing up its worse in the morning when started up struggling to tick over have you any idea what it could be please.
Ricardo
Hi, Magnus i read your instructions, i own a vw tourage 2008, according to the trouble codes i got from dtc the engine has a misfire on all 6 cylinders, and random misfire, one thing that i wonder is that the engine sounds smoothly well tuned, the check engine light is on, I'm replacing the spark plugs they are dirty and according to the a page that i found in Google the gap should be. 036 inch, the old ones were less than the specification gap. Is normal that engines sound smoothly when there's misfiring in all cylinders?
Victor A Thrash
Hi my name is Victor I have a 07 Pontiac Grand Prix V6 I am getting a code low sufficiency threshold have changed wires plugs coils and it runs fine and when I put it under a load start start to run rough so what clean the injectors again it runs fine until I put under load what is the problem
Shaun
I replaced both coils 8 spark plugs and wires still running bad checked my ekg valve it works motor still shakes and body as well could it be a faulty fuel injector I need help
Peter Desravines
Woww wow wow great article! I just realized that 1999 toyota Camry is running on 3 cylinder... By reading your article I'm without any doubt that you're a professional. If you're located in Florida especially in Hollywood, i wanna meet you so i can get my car fixed for good. I really appreciate you, thx for sharing that with us!
Larry
Can a cam sensor make it miss fire on one cyl.
Craig
I have a problem with my Opel Monza GSI fuel injection 1.6 car only revs up to 3000 then back fires and the engine light comes on we change the fuel pump but still nothing any help please
Charl Blom
Hi I have a ford cortina 2l i fit al new parts coil carburetor sparkplugs plugwers dustubetor points condensor and suer of timming slil cant start please can somebody tell me what to do
Alan Ditmore
Thank you for explaining how "misfires" are detected by the camshaft position sensor detecting slight changes in engine speed. I knew my Metro had a burnt valve and low compression, but I would not call that a misfire, since the fuel is burning fine, just leaking into the exhaust and delivering less power. Thus until reading your wonderful explanation, I could not figure out why my computer was calling my burnt valve a "misfire", which I think is a bit misleading of OBD2. Is there any cheap way to improve compression or get rid of the code? cheaper than replacing the valve?
Asser Nirro
I got my Polo 6 TSI 2010 Year model, im very suprisingly without any notice while driving multiples of warning light poped up on the dashboard namely ' ENGINE CHECK ,ABS, EPC, ESP and on a suden the idle of engine have changed, as I try to accelerate i feel engine like jerking , what could cause these and how will fix it??.
bill
good article but didnt cover a p0300 with misfires on all cylinders on 1 bank of a v8. In my case cyl 2 4 6 8 on a dakota 4.7
Greg
Thank you for your help. Has been a great explanation about the theme. Great helpfully web site.
Mack
Yes my car misfire I check the plugs is good bt is still misfire wht can be the problem I already do vavle grainig also it dus not working
Mark Walters
Hi I have a 61 ford falcon 6 cyl has a miss fire under load new coil, plugs, wires points cond, dist, all cyls fire,
Colin
My 206 puegoet starts up fine from cold drives 100 percent problem is when it gets hot will drive it when I switch it off and start it up get miss fire and loss of power so I have to switch it off and start it up after a few tries it's gets back to normal even though the car is hot
GARY MASSEY
My 1997 Sebring run good , as long as I stay under 65 . If I get on the highway at 70 , It does not take long to get the check engine light. Code says multiple misfire's . but I don't feel or hear any misses . Was told it might be the fuel sending unit . Inject not getting fuel , so cylinder does not fire , so get misfire code. Is this possible ?
Magnus Sellén
@GARY MASSEY Yes it sounds like lean mixture caused by either low fuel pressure or vacuum/boost leak. I would start with checking for any leaks around the intake and connect a fuel pressure gauge if possible!
Petrus
Hi Iam driving corsa 1.6 gsi 2002 model, the engine it's got hard start and badly sound idling, need to be rev for idling, when I leave rev cable, the engine loose the idling gose off, again on the spark plugs no1 and no2 there's spark but doesn't ignit the fuel mixer, I don't know what's problem