Car Misfire Spark Plugs

Engine Misfire Symptoms & Causes

In Troubleshooting by 29 Comments

Are you worried that your car is misfiring?

Misfires are one of the most common problems when it comes to modern gas engines.

Many different things could cause a misfire, and it’s not easy to troubleshoot if you do not know where you should start looking.

In this guide, we will go through the most common engine misfire symptoms and the different causes.

Top 6 Engine Misfire Symptoms

There are several different symptoms that you may notice when it comes to engine misfirings.

Here are some of the most common engine misfire symptoms.

1. Rough Acceleration

Car Acceleration

When a misfire occurs, you may feel like light or strong jerk coming from the engine.

These misfires do often come under load from the engine, like when you are accelerating hard. The most common situation to notice misfires is on high gears, low RPM, and the accelerator to the floor. Rough acceleration is a typical sign that your engine is misfiring.

2. Rough Idle

Car Engine Rough Idle E1609793094987

Sometimes, the engine will misfire on idle also; your engine sensors will get faulty values, and the air-fuel mixture will get messed up. This can cause a very uneven idle, which can jump up and down, and the engine may also shut off on idle.

The car engine is most sensitive for small air-fuel mixture problems at idle, so this is probably one of the first places you notice misfires.

3. Vibrations

Car Engine Movements E1609791582981

A car engine is very balanced when manufactured and often has balance axles and different tricks to get as few vibrations from it as possible.

When one or more cylinder is not firing properly, the engine will become unbalanced, and this can cause heavy vibrations inside your cabin on acceleration or at idle.

4. Check Engine Light

Check Engine Light Reset Itself

Modern cars have great monitoring for all the different car sensors on the engine. If one sensor has failed or one sensor picks up that something is not quite right with the engine, it will send the information to the engine control unit.

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When the engine control unit receives the data, it will decide if the problem is severe or not. If the problem is occurring several times, the engine control unit will light up the check engine light to notify you that something is not right so you can get it repaired.

When the ECU notices misfires, it is very common to light up the engine light and store a trouble code on the cylinder which the engine misfired on. Check the trouble codes with a diagnostic scanner.

5. Slow Acceleration

Slow Acceleration

As we discussed before, misfires can cause the O2 sensors to receive faulty information and generate a too rich or too lean mixture.

Overly lean or rich mixtures can cause lowered acceleration and even put your car into limp mode, which will cause the vehicle to not rev over 3500 rpm’s, and it will shut off the boost pressure from the turbocharger.

6. Engine Sound Changed

Car Sound

If you know a little bit about cars, you have probably noticed a difference in sound from different engines. V8 engines have a very different tone than a four-cylinder engine.

If your 4-cylinder engine is misfiring on one cylinder, it may sound like a three-cylinder engine. If your car’s sound is extraordinary, it’s most likely misfires on every cycle that you can hear.

7 Common Engine Misfire Causes

So,  when you suspect that your engine is misfiring, where should you start looking for the problem?

Well, from my experience of over ten years with car repairs, here are the most common causes of engine misfires: Ranked from the most common to the least common.

1. Bad Ignition Coil/Distributor if You Have an Old Car

Three Ignition Coils Vag

The most common problem when it comes to misfires is the ignition coil. Some vehicles have a separate ignition coil on each spark plug, while some cars have one coil with a sparking cable to each spark plug.

Older cars have a distributor and, in some cases, also an ignition coil. If you have separated spark plugs, unplug each coil to see if you can find out if any cylinders are not responding.

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Replace the ignition coil if you find one faulty or have a trouble code stored for one ignition coil.

2. Bad Spark Plug

Spark Plug

The second most common cause of a misfire is bad spark plugs. The spark plugs fire up your cylinders, and they can get worn over time. Spark plugs are often very cheap and, in most cases, easy to replace.

If you can’t remember the last time you replaced your spark plugs, it’s probably time to replace them. If you want to learn a bit more about spark plugs, check this out: Spark Plugs symptoms.

3. Intake Manifold Gasket Leaks

Bad Intake Manifold Gasket

Intake leaks near the cylinder heads are also very common when it comes to spark plugs. This problem was a lot more common in older cars without steel gaskets for the intake.

So, if you have an older engine, you might want to check this. If you have a newer car, it is probably worth checking for any other signs of leaks around the intake manifold gasket or the intake. Check for broken vacuum hoses.

4.  Low Fuel Pressure

Low Fuel Pressure

Low fuel pressure could be caused by a faulty fuel pressure regulator, a defective fuel pump, or a clogged fuel filter. Low fuel pressure will cause a lean mixture in your engine, which will result in misfires on all cylinders.

If you have trouble codes for misfires on all cylinders, you will want to check your fuel pressure. You can find the low fuel pressure causes more in detail in this article: Low fuel pressure causes

5. Injector Problem

Fuel Injector Spray

Another problem, which was more common five years ago, is injector problems. A faulty fuel injector will cause your engine to misfire, and these can be pretty difficult to diagnose without flow testing them.

Injector problems are not very common on newer cars, and because of this, you want to check out the other possible causes first, but it is absolutely worth checking.

6. Low Compression/Damage Inside the Engine

Car Compression Test

If you have checked everything else, there is a big risk that your engine has low compression or other damage inside your engine.

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A faulty timing belt adjustment could also cause low compression, resulting in misfires. If you know that the timing belt was replaced recently, you should double-check so this person installed it correctly.

7. Wrong Air-fuel Mixture

Misfires can also be caused by a faulty air-fuel mixture sometimes. Many different sensors can cause a faulty air-fuel mixture in your car, like the MAF sensor, O2 Sensor, Coolant Temperature sensor, and more.

What is a Misfire?

Misfire

To find out what a misfire really is, we have to go through the car engine basics first. Here you will see a good picture of how your pistons and crankshaft are moving inside the cylinder when your engine is running. The pistons are pushed down by an explosion inside the cylinder.

When the piston is pushed down, the crankshaft is spinning. The engine is working in four steps; that’s why this engine type is called a four-stroke engine.

  1.  The piston goes down, filling the cylinder with an air-fuel mixture from the intake
  2.  The piston goes up, compressing the air-fuel mixture to a high pressure
  3.  The ignition from the spark plug is igniting the air-fuel mixture and the explosion is pushing the piston down and rotating the crankshaft
  4.  The piston goes up, emptying the burned air-fuel mixture through the exhaust pipe.
  5.  Repeat the process from step 1

That’s the function of a four-stroke engine that is fitted in almost all modern car engines.

A misfire occurs when ONE or more of these stages is wrong or missing

  • An overly lean or overly rich air-fuel mixture
  • Bad ignition spark / Wrong timing of the ignition spark
  • Low compression / Air-fuel mixture is leaking out
  • The timing of the inlet/outlet of the air-fuel mixture is wrong

With that knowledge, it’s a lot easier to find the problem that is causing your misfires. As you can see, in theory, there are not a lot of things that could cause a misfire.

But when you start to diagnose your car, you will realize that it is not always as easy as it looks to find the problem.

29 thoughts on “ Engine Misfire Symptoms & Causes ”

Comments
  1. 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 ?

    1. Author

      @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!

    2. 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

  2. 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,

    1. 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

  3. 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

  4. 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

    1. Thank you for your help. Has been a great explanation about the theme. Great helpfully web site.

  5. 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??.

  6. 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?

  7. 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

    1. 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

  8. 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!

  9. 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

  10. 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.

    1. 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?

      1. 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

  11. 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

  12. 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

  13. 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,

  14. 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.

  15. 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 ???

  16. 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

  17. 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?

  18. 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?

  19. My toyota vitz 2nz engine still misfiring even after puting new plugs wat can b the problem

  20. 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

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