Lexus calls for changing the spark plugs at 60,000 on your IS350 - here's what you'll need to change the spark plugs on your IS350:
-10mm socket set with at least a 6 inch extender bar
-Spark plug socket
-A tiny bit of motor oil
-If have you a ratcheting wrench or a universal joint, it will very much come in handy.
-A 6-pack of your favorite beer
You'll need 6 spark plugs - I used the OEM Denso plugs, Lexus part # 90919-01249:
These plugs come pre-gapped, so if you're using the OEM Denso Iridium plugs DO NOT adjust the gap on these plugs.
First you'll want to remove all the engine covers, along with the air intake box assembly, air hose, and induction scoop.
This is what the engine bay should look like after removing everything. In the picture below, I'm pointing to one of the ignition coil tubes that we're going to remove a few steps later. Take your time and get familiar with what they look like and locate all 6 (3 on each side), because there will be a few harnesses in the way that will have to be loosened in order to remove the ignition coil assembly:
I started with the passenger side. There are a few 10mm nuts that are fastening a harness over the ignition tubes, partially blocking access. Remove them:
Next loosen the 10mm bolts fastening the tubes to the engine block.
Separate the harness from the ignition tube by pressing on the tab and pulling the two apart:
Pull the tubes upward and out.
You'll now be able to see the spark plug inside the shaft.
Now you'll need your spark plug socket with the 6" extender bar. The spark plug socket is a special deep socket that has rubber grommets inside that will grab the spark plug and let you remove it from inside the ignition shaft:
This is what the whole thing looks like:
You're going to need every bit of that extender bar to remove the plugs:
This was the first plug I removed (at 60,000 miles)
Apply a tiny bit of clean motor oil to the first three threads of the new spark plug to help avoid cross-threading the plugs. Be VERY CAREFUL installing the plugs - if you cross-thread the plugs, you now have a very big problem. Put the new plug into the same special spark plug socket tool you used to remove it, lower it into the shaft, and hand-tighten it once the plug finds the thread:
Use a torque wrench to tighten the spark plugs to 25 N*m (254 kgf*cm or 18 ft*lbf).
Reinstall the ignition coil tube, and repeat for the other 5 tubes. The bolts that fasten the ignition coil tubes to the engine block should be torqued to 10 N*m (102 kg*cfm, 7 ft*lbf). In other cars I've done this on, you had to make sure to do one plug at a time because you didn't want to connect the wrong ignition coil onto the wrong spark plug and foul up the firing sequence. On this car you can do as many as you want at the same time because the harnesses are just long enough to reach the intended plug - so no worries there.
Now on to the driver's side. This side will be a little more difficult as there are a few wiring harnesses that must be removed in order to gain access to the bolts that secure the ignition tubes. Start by removing these two nuts:
You can then lift the harness out of the way just enough to slip a box wrench (the ratcheting type will make your life a whole lot easier) behind and unfasten the ignition coil tube:
Remove or loosen any wiring harnesses that impede your access to the ignition coil tube bolts. The final bolt can be accessed from above with a little elbow grease:
Reinstall everything you just removed, and enjoy a (few) well deserved beer(s) for a job well done. You might want to take this opportunity to remind the significant other of your money-saving accomplishments. Make sure and let her know you just saved $300.
I hope you all find this useful!