My 2017 Kia Optima LX with the 2.4L Theta II GDI engine has repeated engine misfires caused by oil-fouled spark plugs. The engine burns 1 to 2 quarts of oil every week on only 200 to 250 miles of driving, 4 to 10 quarts per 1,000 miles, far above the 1 quart per 1,000 miles threshold in Kia's own TSB ENG222. Every time the spark plugs are removed, they are coated with oil. Cylinder #4 has misfired three times in five months (June 5, August, and November 2026), and cylinders #2 and #3 misfired on June 17, 2026. All...
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four ignition coils and spark plugs were replaced in August 2026, and the #4 misfire returned within about three months. We have paid out of pocket for repeated repairs since January 2025. The KSDS update was installed at a Kia dealer. The vehicle is now unsafe to drive because misfires can cause sudden loss of power at highway speed, and running low on oil risks engine bearing damage and seizure. We have taken it out of service. I have written to Kia America's executives requesting diagnosis under TSB ENG222 and repair under the Theta II settlement's lifetime warranty. I am asking NHTSA to investigate excessive oil consumption and repeated oil-fouled spark plug misfires in Theta II 2.4L GDI engines in 2016-2020 Kia Optimas.