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Kia Optima Spark Plugs Replacement Guide
How to check or change the spark plugs in a 2016 to 2020 Kia Optima with the Theta II 2.4L GDI I4 engine.

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Paul B. Michaels
Author & Photographer
Auto Mechanic Since 1989

2019 Optima 2.4L I4
Pull Off Engine Cover
Release Friction Fasteners
This automotive maintenance tutorial was specifically written to assist owners of the 4th generation (2016, 2017, 2018, 2019 and 2020 model years) Kia Optima sedan in checking or changing the spark plugs in the Theta II 2.4 liter GDI inline four cylinder engine.

Owners of other Kia, Hyundai or Genesis vehicles such as the Niro, Sportage, Sedona, Telluride, Sorento, Rio, Forte, Soul, K900, Cadenza, K5, Stinger, Tucson, Santa Fe, Kona, Palisade, Elantra, Sonata, Accent, Veloster, Ioniq, Nexo, Venue, G70, G80 and G90 may also find these DIY instructions to be helpful.

The OEM (original equipment manufacturer) laser iridium spark plugs that were in this 2019 Kia Optima LX FE were part number NGK SILZKR7E11 (also known as SILZKR7E-11 or SILZKR7E 11 or 92315).

A few other compatible replacement spark plug with their part numbers are as follows: NGK LKR7DIX-11S (93175), Autolite APP6203, Champion 9047, Autolite XP5702 and Kia 18849-11070.

The tools needed to complete this procedure include a 10mm socket with a 1/4" drive ratchet, a 5/8" spark plug socket, an extension bar, a 3/8" drive ratchet and a tube of dielectric grease.

The first step is to open the hood.

Then carefully pull the black plastic cover off the top of the engine by lifting up each of the four corners separately.

The cover is held in place by four rubber friction fasteners attached to metal pegs on the top of the engine.


Engine Cover Removed
Top of Engine Exposed
Four Ignition Coils
Set the engine cover aside in a safe place.

Once the cover has been removed, you'll be able to see the four black plastic ignition coils.

If you have access to compressed air or a wet/dry shop vacuum, thoroughly clean off the top of the engine to help reduce the risk of having debris or a foreign object from falling down into the spark plug well.

Electrical Connector
Slide Out Grey Lock Tab
Push In Release Button
I also recommend only checking or changing one spark plug at a time to further reduce the risk of having something fall down into the cylinder.

Slide back the grey locking tab on the ignition coil's electrical connector.

Push in the release button on the electrical connector before pulling the power plug straight off the ignition coil.

Disconnect Power Plug
Loosen Counterclockwise
Ignition Coil Bolt
Loosen the single bolt that secures the ignition coil to the top of the engine valve cover by turning it in the counterclockwise direction with a 10mm socket and a 1/4" drive ratchet.

Spin out the bolt the rest of the way by hand.

Set the bolt aside in a safe place.

Lift Out Ignition Coil
Old Spark Plug In Well
Spark Plug Socket
Rotate the ignition coil back and forth a few times to make sure the rubber boot isn't stuck or "frozen" to the top of the old spark plug if they have not been separated for 100,000 miles or more.

Pull the ignition coil out of the spark plug well and set it aside in a safe place.

If you have a CEL (check engine light) or SES (service engine soon) warning on your gauge cluster, use an OBDII scanner (also known as an "OBD2 scan tool") to check for an ignition coil related DTC (diagnostic trouble code) such as P0350, P0351, P0352, P0353 and P0354.

The OEM (original equipment manufacturer) Hyundai / Kia ignition coil part number is 27300-2GGA0.

(I recommend checking the condition of the spark plugs after about 60K miles and again at 90K miles when they are close to their service interval replacement at 105K miles.)

Attach the 5/8" spark plug socket to a long extension bar and a 3/8" drive ratchet.

I like to secure the socket to the extension bar with some painter's tape to make it doesn't pop off and become stuck down in the well.

Loosen Old Spark Plug
Lift Out Old Spark Plug
Inspect Old Spark Plug
Lower the socket down into the well and push it on to the top of the old spark plug well.

Carefully loosen the old spark plug by turning it in the counterclockwise direction.

If you have trouble loosening the old spark plug due to corrosion (rust) or debris buildup, try spraying a very small amount of penetrating oil down into the spark plug well.

Allow the penetrating oil to seep into the threads for at least 5 to 10 minutes.

Once the old spark plug is loose, detach the ratchet from the extension bar.

Spin out the old spark plug the rest of the way by hand.

Lift the extension bar and socket out of the well.

Detach the old spark plug from the socket.

Inspect the old spark plug for any signs of damage or abnormal wear.

If the old plug appears to be burnt or covered in soot or oily sludge, the engine may be burning oil and should be inspected by a professional mechanic.

If the electrode tip on the old plug appears to be burnt or covered in white powder, the engine may have been subjected to overheating. You may need to choose a spark plug with a different heat range (colder or hotter) for your climate.

Empty Spark Plug Well
Lower In New Spark Plug
Tighten Clockwise
If you have a spark plug gap gauge tool, check the gap on the new spark plugs to make sure they match the manufacturer's specification listed on the box.

Iridium spark plugs can not be re-gapped. So if the gap isn't correct, the new plugs should be returned or exchanged.

The OEM NGK SILZKR7E11 plugs should be gapped to 0.044".

(Most spark plug manufacturers recommend that you do NOT use anti-seize lubricant grease on the threads of the new spark plugs since it can easily lead to over tightening.)

Push the new spark plug into the socket.

Your socket should have a rubber insert or a strong magnet to hold the spark plug securely in place.

Carefully lower the new spark plug down into the well and spin it in a few turns by hand in the clockwise direction to help prevent it from becoming cross threaded.

Continue tightening the new spark plug in the clockwise direction with the 3/8" drive ratchet to a small fraction of a turn past finger tight.

If you are installing new spark plugs, you may feel the new crush washer collapse as you are tightening the plugs.

If you are re-installing the old spark plugs after inspecting them, just tighten the old plugs to a small fraction of a turn past finger tight.

If you would like to use a torque wrench to tighten the spark plugs, the service manual specification is 10.8 to 18.0 lb-ft of torque (14.7 to 24.5 Nm).

Double check that the new spark plugs are tight before moving on to the next steps.

Apply Dielectric Grease
Lower In Ignition Coil
Spin In Ignition Coil Bolt
To help ensure a reliable electrical connection, apply a small amount of dielectric grease around the opening in the rubber dust boot at the bottom of the ignition coil.

The dielectric grease will also help keep out any dust, debris or moisture.

Lower the ignition coil down into the spark plug well.

Push the rubber dust boot over the top of the new spark plug.

Rotate the ignition coil back and forth a few times to help spread the dielectric grease.

Line up the bolt hole in the ignition coil with the corresponding hole in the valve cover.

Spin in the bolt a few turns in the clockwise direction to make sure it doesn't become cross threaded.

Tighten Bolt Clockwise
Push On Power Plug
Slide In Grey Lock Tab
Tighten the ignition coil bolt by turning it in the clockwise direction with the 10mm socket and a 1/4" drive ratchet until it is snug.

Try to avoid over tightening the bolt to prevent from cracking the plastic ignition coil housing.

Push the electrical connector straight into the socket on the ignition coil.

You should feel or hear the power plug "click" securely into place.

Slide the grey locking tab in towards the ignition coil to secure the electrical connector.

Ignition Coil Secured
Push On Engine Cover
Spark Plugs Replaced
Lower the plastic cover back into place over the engine.

Firmly push on the cover to secure the four friction fasteners on the underside of the cover to the metal pegs on the top of the engine.

Start the engine and listen closely for any strange sounds that might indicate a problem such as a loose spark plug or a disconnected electrical connector. If you do hear an odd noise, immediately turn off the ignition and check your work.

(The service interval specification in the owner's manual for replacing the spark plugs is every 105,000 miles or every 7 years.)

Be sure to write down the spark plug change in your vehicle's service records.

Please check out all of my 2016-2020 Kia Optima DIY Repair & Maintenance Guides.

If you found this guide to be helpful, please consider making a small donation by clicking on the "Donate" button located to the right of this paragraph. Thank you!
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