DIY Repair for Engine Misfires

Asked by alanrrios Aug 07, 2019 at 04:13 PM about the Kia Rio

Question type: Maintenance & Repair


I have a 2006 Kia Rio that is currently experiencing some engine issues. A diagnostic at Auto Zone confirmed the issue is with 2 out of the 4 cylinders misfiring. I've done a bit of research and so far this seems like something I may be able to resolve myself. However, I would like some assistance in diagnosing the issue to make sure I am not in over my head.

I first noticed the issue because my car was slow to accelerate. It felt as if the engine was significantly weaker. I checked my engine oil, because I wasn't sure where else to start, and noticed it was really low even though I was not due for an oil change. I went to nearby shop and they took note that there oil leaking over the top of the engine and most likely the culprit of the leak. I've since added oil to the engine but it is still bad. After receiving some advice from a bystander they recommended I go to Auto Zone for a diagnostic. Auto Zone confirmed my engine had a couple of misfiring cylinders.
The bystander's advice was that it could be a fuel injector problem due to the engine spitting oil.
The representative at Auto Zone mentioned that it could be an issue with spark plugs. When I mentioned the ignition coils they let me know that it could be an issue with the ignition coils being covered with oil.

I haven't done TOO much research but I've considered a few solutions. Those are as follows, in order that I would want to try:

1.) Clean the ignition coils so that there is no oil present.
2.) Replace the ignition coils where engine misfire is present.
3.) Get an expensive diagnostic from a mechanic to ensure there is no other issues such as a fuel injector problem and then follow it up with an expensive repair.

My goal with this post is to get more advice on the issue so that I can make a better decision on how to continue. My biggest gripe with this now is how this issue could have started. If I were to replace the ignition coils without addressing the issue that caused the ignition coils to have issues in the first place, such as what caused them to get covered in oil, then I would have spent money on a repair that didn't address the underlying issue.

Best case scenario is that cleaning the engine coils and making sure they are free of oil fixes the problem. Worst case scenario is that I need to get a diagnostic done to find that there is a deeper, more expensive problem.

Thank y'all for your assistance.

2 Answers


Remove the ignition coils and replace the spark plugs at a minimum. Inspect Ignition coil #2 and #4 for oil. You might want to consider replacing the valve cover gasket if the oil is really bad. You can swap the coils from one cylinder to another and see if the CEL stays on and if the misfire codes move from cylinder to cylinder. Then you know it is the coils.

1 people found this helpful.

I took your advice and switch engine coils 1 and 2 at home before heading to Auto Zone for an updated diagnostic. The car was still rough while idle and felt different while riding. At Auto Zone the updated diagnostic showed that only cylinder 4 was misfiring now. I switched 3 and 4 there and got an updated diagnostic. At first it was all clear but when I accelerated to leave the parking the rough ride started again. The last diagnostic showed that cylinder 3 was now misfiring. All engine coils were still covered in oil. I was not able to figure out an answer of where that oil would be coming from and if it would require a more intensive fix. So to recap: Swapping engine coils 1 and 2 fixed the cylinder 2 misfiring issue on 2. Swapping engine coils 3 and 4 confirmed issue with single engine coil now on cylinder 3. I will be continuing by buying a new engine coil online and swapping it out.

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