Tutorial: How to Change your Spark Plugs - Lexus IS Forum
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post #1 of 14 (permalink) Old 02-27-2005, 06:27 PM Thread Starter
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Install Guide Tutorial: How to Change your Spark Plugs

Difficulty: Intermediate / Mechanically inclined

Time: 4-6 hours (your first time around at least)...maybe less with this tutorial as a guide

Interval: About every 60,000 for NA and about every 10,000 for those with F/I is preferred.

Tools Required or used to assist:

-1/4" rachet

-1/2" rachet

-Long extension

-Short extension

-3/4" (I believe, the normal sized one, not the huge one) spark plug socket

-Needle Nose pliers

-Flat head screw driver

-Adjustable pliers

-8mm socket

-10mm socket

-12mm socket

-#5 Hex Wrench

-12mm wrench with closed end on one side

-Spark plug gapper tool with wire gap checker


Suggested extra tools:

-Mechanix Gloves

-Magnetic nut retriever

Procedures for replacing spark plugs (NOT EVERYTHING DISCONNECTED/REMOVED HAS A PICTURE):


#0: Park in an area out of the elements, open the hood and ensure you have enough light.

#1: Disconnect the negative side of the battery terminal.
#2: Disconnect at least one side of the front sway bar (if present).

#3: Disconnect and remove your upper intake piping going into your throttle body. Don’t forget to unplug the Mass Air Flow (MAF) sensor wiring harness…most importantly, do not forget to reconnect it when you’re all done!!! That was the only thing I forgot when I did this and a CEL came on during initial startup. The CEL goes off on its own when you connect the MAF harness.

#4: Disconnect the throttle cable and pull the cable out of the holding bracket completely (you do not have to undo the screw in the back like I did).

#5: Disconnect the x3 wiring harness going to your throttle body

#6: Unscrew top left bolt going into your TB ***IF*** you have a grounding kit wire going to it.

#7: Disconnect x2 coolant lines going to your TB…don’t worry only a couple drops of fluid come out. Note: Be careful not to tear any tubes. It helps to use a flat head to push the tube out by inserting the flathead in-between what the tube connects to and the top of the tube (after pulling away the hose clamp obviously)

#8: Take off TB bracket that is just underneath the intake opening that your intake piping plugs into. Note: You will not be able to completely remove the TB and upper intake together without removing this if you have a turbo that sits high due to tubular manifold…otherwise you may be able to keep that bracket on there, not sure. Either way, pay attention to that. DISCONNECT the bracket that holds one of your wiring harnesses attaching to the TB in the back to the left of the throttle assembly.

#9: Disconnect the x4 of x5 vaccum tubes that are attached to your upper intake, most are in back. The remaining one that you will not be able to reach yet is the skinny one under the intake.

#10: Unbolt the x4 bolts (upper) and x2 nuts (lower) securing your upper intake to your lower intake. Be careful not to damage the gasket. The nut at the bottom on the backside can only be reached with a wrench, or if you have a flexible socket.

#11: Pull the upper intake off, being careful not to pull too far without disconnecting that last x1 of x5 vacuum tube that is attached on the bottom. Disconnect the tube.

#12: Inspect all the way around to ensure you disconnected everything, then slowly pull the TB and upper intake completely off and set to the side.

#13: Use your #5 hex wrench to take off the timing belt cover.

#14: Un-screw x3 bolts holding on the black boxes (I forget what they’re called) in-between your spark plug wires and remove those.

#15: Pull out the x3 spark plug wires…remember where everything came off. Wire order from front to rear is 1,5,3 (for the spark plug wires)

#16: Check to see if you have (oil, tranny, brake, etc. fluid) spillage inside the spark plug wells so when you start taking out spark plugs, you don’t get worried if you see oil inside, thinking it’s coming from your cylinder. NOTE THE OIL SPILLAGE INTO MY SPARK PLUG WELL.

#17: Use your spark plug remover with long extension and ½” rachet and pull out all x6 spark plugs.

#18: Inspect your spark plugs for signs of anything bad going on with your engine (refer to Spark Plug section of FAQ for pictures on what they should/shouldn’t look like).

#20: Check the gap in your old spark plugs to make sure you know what you’re supposed to gap the new ones at.

#21: Check/Change the gap in the NEW spark plugs (using a wire gap space checker and gapping tool)…also ensure that the ground electrode lines up with the center electrode and isn’t pushed to one side or the other a little.

#22: Go from #17 back to #1 in reverse order.

#23: Double check all of your work, ensuring all tools are out of the engine compartment. Don’t forget to reconnect the MAF sensor wiring harness.

#24: Start the car to make sure you don’t have a CEL and everything is 100%.

Last edited by IS300AllShow; 02-27-2005 at 07:33 PM.
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post #2 of 14 (permalink) Old 04-06-2008, 08:33 PM
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This guy right here saved me 300$ on a last-minute decision to just do it myself and the pictures and info and process here is right on. Thank you so much for the help. More people should be this accurate. Big ups to this guy.
Kicker3303 is offline  
post #3 of 14 (permalink) Old 02-07-2009, 06:13 PM
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Thanks For The Info. Saved Me Some Bucks
JHREYES is offline  
post #4 of 14 (permalink) Old 06-11-2009, 10:04 AM
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Wow! What a long process! +rep for so much detail.
El-Bori is offline  
post #5 of 14 (permalink) Old 06-15-2009, 11:42 PM
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Rep to the fullest. This is a great write-up. Hopefully, I can get this knocked out in about 2hrs.

o3' Graphite Grey Turbo IS300 w/ 6spd swap, ProEFi128, T6765 Billet, stock head
Going to throw a Supra tranny (V160) into your IS? Got questions? Feel free to ask me.
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post #6 of 14 (permalink) Old 09-21-2009, 06:01 PM
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I'm doing this job right now and would like to know if I have to change the upper intake gasket for a new one each time I replace the spark plug ???

Thanks for your help!!
MANU_IS_300 is offline  
post #7 of 14 (permalink) Old 11-06-2009, 02:18 AM
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I used your guide yesterday, -SuperleX-iS-. Thanks a lot for saving me the time of figuring it out myself, and saving me some $$$.
SilverIsMy300 is offline  
post #8 of 14 (permalink) Old 01-24-2010, 08:03 PM
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I thought spark plug comes pre-gapped for you? Why do you have to gap them yourselves?

'03 IS300 SD TCM 5-SPD LSD
tonynca is offline  
post #9 of 14 (permalink) Old 01-25-2010, 03:48 PM
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you certainly at least want to make sure that they are properly gapped.

Have a question? Try the my.is FAQ or, if you can't find an answer there, search before posting your question (hopefully in the correct forum).

2002 IS300 5mt. MSM stock for now
Cobra Project:
FFR MKIII '65 Cobra Replicar - 427 cid V-8 (thats 7.0 liters) engine 525hp/520lb-ft torque at the flywheel (and this is in a 2200 pound car) Painted Lexus Spectra Blue Mica with GM Arctic White stripes -- now street legal
longnights is offline  
post #10 of 14 (permalink) Old 05-08-2010, 06:58 PM
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Question: Do the spark plugs need o-rings or some type of gasket? Mine were covered in oil and now that I changed them I have 2 misfires.
Co0kieMonster is offline  
post #11 of 14 (permalink) Old 07-07-2010, 05:49 PM
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Great write up! I'll be changing my plugs this weekend. One question though, why can't I ever see any pictures on this forum?
ColtonA7X is offline  
post #12 of 14 (permalink) Old 09-12-2010, 07:57 PM
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Quick question: When replacing the plugs, I noticed that one of the plug wires (not coils) wouldn't really "click" onto the plug no matter how hard I pushed down on it. Is this a common problem and should I be worried? If so, can I replace the wire alone or do I need to buy the coil and wire together?
i3igpete is offline  
post #13 of 14 (permalink) Old 09-19-2011, 10:08 PM
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How often are you supposed to change the coil pack?
lexus5712 is offline  
post #14 of 14 (permalink) Old 05-06-2012, 06:31 PM
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Thanks Yo!

Just knocked it out in 2Hrs 10 Min!!! Thanks for the tips yo!!
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