R4a2m0o

I just became a member here, and I don't know if you have tech articles somewhere, but I find it very useful when people buy new cars to have some quick guidelines on how to do certain jobs. I just changed my plugs today and I thought I'd share how I did it.

Time: 1-2 hours depending on smoke breaks etc.

Tools: 10mm wrench, deep and short sockets, ratchet, spark plug socket (small type), various extensions long and short, antisieze, dielectric grease.

First of all make sure you have the right plugs with the correct gap (do not try to gap iridium spark plugs unless you are superman and can bend the ground electrode with your finger). I used NGK Laser Iridium. Original plugs are Denso IR.

Start by removing the plastic engine cover held on by two clips and 2 10mm nuts.

This car has a coil-on-plug ignition setup so there is no wire to deal with and you can immediately see that on the driver side without removing anything else. Simply remove the one 10mm bolt holding each coil to the valve cover, and pull it out for each plug. I found that using needle nose pliers made removing the electrical plug much easier. There may be some tight areas against the side of the engine bay, so get creative with extensions, u-joints, or whatever you can use to allow you to insert and remove the plug, socket, and extension without brute force and ignorance.

At the end of the day, I had to remove the black box "thing" connected to the intake tube to get at the passenger side valve cover. To do that I removed one 10mm bolt holding the box down and two 10mm hose clamps on the airbox and throttle body and pulled the whole assembly out. After that you have a ton of room. I also had to move a small bracket held on by a 10mm bolt and 10mm nut on the passenger side to get the second coil from the front. You will see it. I found that putting the back end of my extension under the plastic shock tower cover thingamagigs allowed me to get a straight shot to the plug well without forcing it for about 3 or 4 of the plugs.

For the farthest plug back on the passenger side, I just pushed the battery box in a little bit rather than removing it. It does no damage to the box if you are careful and saves you a bit of time.

When the plug go in, make sure you have some antisieze on the threads. This helps the next time they have to come out. You can also put some dielectric compound to seal the porcelain to the wire boot but it's not absolutely necessary since the whole thing is sealed with rubber gaskets. If you do, make sure it doesn't come in contact with the contact area. Turn the plugs in by hand until you get to zero lash where the gasket starts to crush, then hook up your ratchet.

When you turn it with a ratchet you will feel the crush washer start to crush. You will reach a point when the resistance goes up. Just give it a tug or two at that point and it will be close to where you want it. If you are **** or haven't installed a million spark plugs, get a torque wrench or follow the plug manufacturer instructions.

Put it all back together, say a prayer and feel the difference!

AlexusAnja

The single most important step in DIY spark plug removal/installation. So many a block or plug have been damaged because they put the plug to the ratchet and immediately start ratching away when they've been off thread. The of course either the plug gets wrongly threaded or the block is messed up, and worse, the metal filing falls into the cylinder block. Ugh... not a pretty sight.

Excellent writeup and it looks to be a 100% easier job to do than on the RX300 I have. 4-hour killer that I would never do on my own.

R4a2m0o

Thanks! Plugs are very easy to start incorrectly and after that it gets very messy... thread chasers, taps with grease in the flutes... not fun at all. On this car the plugs are very easy to start by hand, but I have worked on several overhead valve engines that were a pain in the ***.

intermec

it will be nice if there are pictures, especially for people (myself) who can only learn by looking at something.
Good post, thanks

cincin

Nice write up.

docbruce19

Thanks. Nice guide. Will probably go the **** torque wrench route. My 2002 LS430 now has almost 103k miles and will be due for a plug change at 120k. Mileage is still good, no performance issues. Starts easily. The owners manual states 120k mile interval with a little note that it is required by the emissions warranty, as if it really isn't important? Beats the old days when we had to change plugs (and points!) every 12k!

warminwisc

I saw on autoweek or something, on the 125 k plugs crack em and start the engine and turn it off and proceed with removal. I guess you will be less likely to draw some carbon up onto the threads in the head.

docbruce19

I saw the AutoWeek video too. I think the reason for just barely cracking the plugs open, starting and revving the engine once and shutting down is to break any carbon on the part of the plug in the combustion chamber off into the cylinder and prevent ruining the threads of the head.

striderg3

is it the same procedure to change GS430 2006 / 07?

Gene01

Great writeup.
I would just add that there is a debate regarding the use of anti-seize. Both Lexus and the plug manufacturer recommend against it.

Legender

I use an old rubber spark plug tube off my daughter's Honda. Fits the plug well and the rubber grip on the top side allows me to easily turn the plug without the excessive weight of the socket and extension. Gives me a better feel for the threads going in the right way.

TheLexor

Great write up! Regarding r/r of plugs themselves: once they are loose through use of ratchet and socket, I use a length of about one foot gas line hose to insert over the ceramic. This works well when plugs are not extremely tight and when engine is cool. The rubber hose also works well when trying to remove a plug that has fallen off the socket. When reinstalling plugs, I carefully insert the hose onto the ceramic and guide into the socket well and feel for correct insertion and threading. Once I am sure the plug is threaded correctly, I just plug the hose from the plug and finish with a conventional socket and ratchet. Sorry, no pics, but you should get the idea. BTW-if you try changing plugs with a warm engine, the hose will prevent potentially burning fingers and hands.