2010 Suzuki SX4 persistant misfiring

I have a 2010 Suzuki SX4 that has had a persistant electrical/cylinder misfiring issue all year. It started as a misfire code, so i changed all the spark plugs. Runs fine for a few weeks then begins misfiring again. I changed the ignition coils twice this year and the spark plugs three times. Every mechanic I take it to either says its fine or just wants to change out the plugs/coils again without looking for the issue that is causing them to burn out. But i know its not the parts, its something affecting the parts, some under lying cause. The plugs in the picture only have a few months of use on them and you can see they are burnt already. I live in a small town so i exhausted the mechanics i can take it to, and i only have a small amount of experience with working on cars. Would a bad alternator cause this? Is there too much power being sent to the cylinders, or too little? Any advice on a direction to go in solving this problem would be greatly appreciated. What would cause my plugs/coils to keep burning out, causing misfiring and the engine running rough?

Just a wild guess…are you using the correct spark plugs for the vehicle/engine?

Sometimes there can be just a “digit” difference between engines, year models, etc.


Did you check the gap on the new spark plugs prior to installation?



Did the new coils come with new boots?


Yep, like i said its not the parts im putting in, its something causing them to go bad quickly

Showing the outside of the plugs don’t tell me anything. Show the tips that go inside the engine…

Does the engine use oil? How many miles on it? Has a compression test been done?

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I’m of the opinion that when a performance problem exists that a compression check should be performed. The spark plugs are out so verify any potential engine mechanical faults at that time.

What can happen is that low compression can affect new spark plugs after a certain amount of time. The car is a 2010 but the miles on it (which are not always relevant) are not provided.

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Your problem is not a car problem, its the fact that you live in a small town without any really sharp mechanics.

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90,000 miles. the problem is deffinately electrical, But now that several people have brought up the spark gap im going to check that again, but i dont trust the mechanics that installed them, since they were the ones telling me nothing was wrong with it. I’m pretty sure they used pre-gapped spark plugs set to 1mm, but i just looked it up and the car is supposed to have them set to 0.044. Could too big a gap on the spark plugs be the cause of all my problems?

Sure could. It could also cause early coil failure.


1 mm is 0.040 inches… you are fine. A wider gap can put more stress on the coils.

Based on what data, knowlege and experience?

What you describe is textbook (and my personal hard knocks) symptoms of an engine fouling its plugs.

So show me a picture of the plug tips and tell me the results of a compression test to prove me wrong.

Im sorry im not trying to say you are wrong im just a guy that doesnt know how to fix cars and it just seem electrical to me because every time new coils and plugs are put in it runs fine until they burn out. I’ll try to get a picture of the tips, but im at work at the moment.

The difference between 1mm (.039”) and .044” is .005” (.12mm) which is insignificant, and not likely to be causing your problem. But I am still curious as to what the problem is. I used to have an 02 Camry with similar symptoms. After about a year of not solving it I just gave the car away to a friend who needed a car like NOW! After 5 years car still has same problem at over 225k miles.

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You say it’s “definitely electrical”. That’s a pretty strong statement considering that you, and the shop, does not even know what the compression is. Hopefully there is not a compression issue but at this point it’s an unknown.

The plugs are out so why in the world not verify top end condition at that time since they were 90% of the way there anyhow?

As for mileage, 90K is plenty enough miles for things to go wrong and I have seen many, many engines with serious compression issues at less than 25k miles. The poster child for that issue was a 6 month old Subaru which had less than 60 PSI on all 4 cyls and the car only had 7k miles on it.

My point here is that IF there is a compression issue you could be throwing plugs at that vehicle forever without solving anything. The plugs would be the symptom; not the cause.

It’s not the plug gap. 1 MM is roughly .040 and if they’re at .044 that insignificant difference is not going to matter. Matter of fact, a wider gap creates a hotter spark and can have a tendency to eliminate a miss instead of creating one.


im sorry i mispoke when i said deffinately electrical. Its just seemed that way from what the guys were telling me at the shop. They said it could be the cars computer. but apparently they were just spit balling.

If they are saying computer then I feel their diagnostic skills might be a bit shallow; or non-existent. When someone says computer it smacks of wild guessing.

As for compression readings there is a rule of thumb. The compression ratio on that vehicle is 10.2 to 1. This means that a good compression number is roughly 20 X the compression ratio (at sea level) so somewhat over 200 PSI. Allow for miles, wear, and altitude, and what you really should look for is something in the neighborhood of 180-190 on all cylinders.





thank you all for setting me in this direction, i suppose i will have to research compressing testing now and what the heck to do after to fix it

@Tester ,
Great site thank you.

this is what another person told me:

The plugs and coils are not burning out. There is an issue in the circuits that control the coils, assuming this is actually an ignition issue and not a fuel or compression problem which it very well could be.

More likely this is there is a wiring or computer problem. There is a common power supply to all coils and individual trigger wires that go to the computer and are operated by a final transistor in the PCM.

There can be a bad connection at one of the wiring plugs, a shorted wire in the harness or even a problem with the transistor in the PCM.

You are going to need a specialized Auto Electric shop to diagnose this properly.