Changing Spark Plugs on an IS200

steviewevie

09-05-2016, 08:56 AM #1

Here's a step-by-step guide to replacing the spark plugs on an IS200. I was changing from the OEM plugs to Denso IK20 iridium plugs. These aren't as long-life as the OEM plugs but supposedly are slightly higher-performing plugs. Since the IS200 has a 6-cylinder engine, you'll need six new plugs. Here are the ones that I bought (off eBay US) :

[Image: plugs1.jpg]

The following instructions are all for a normally aspirated (i.e. standard, no supercharger/turbo) car. You may need different plugs for other types of installation.

You will need a 10mm hex socket and a 16mm spark plug socket or spark plug wrench. You will also most likely need a socket extension since the plugs are actually located quite deep, so a spark plug socket and extension is probably a better option than a plain plug wrench.

ok, let's get started. Here's the engine bay, and we first need to take some covers off :

[Image: plugs2.jpg]

First of all, remove the air filter. This is housed under the "stripes" with the Lexus logo in the middle of the airbox (the big black plastic thing). There are two clips, one at each end of this long thin section. Release both of the clips and the air filter easily pulls up and out. I have a K&N filter so it might look slightly different to yours, but the shape will be the same :

[Image: plugs3.jpg]

Now we need to remove the airbox and the air inlet (the bit at the front of the car that sucks in the air). These two big pieces of black plastic are held down by 10mm bolts. It's probably easier to remove the air inlet first, which has three bolts, and then the airbox itself, which also has three bolts. When you've got the bolts out of the airbox, it might still feel like there's a bolt left, because it won't come off that easily. It's joined onto the throttle body on the top of the engine still, but a firm tug (not too rough though !) should ease it off. Remove the small hose that plugs into the left of the airbox by pressing on the clip to release it.

Now you will be able to see the top of the engine, but there's still another cover to be removed, the small one on the left with the "VVTi" lettering on it :

[Image: plugs4.jpg]

IS200 Turbo project now just about complete ! See my thread here and leave your comments.
Now running standalone Syvecs ECU and no stock ECU !

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steviewevie

09-05-2016, 08:56 AM #2

That cover is held down by four 10mm bolts, remove those and this final cover lifts right off, and you're left with something like this :

[Image: plugs5.jpg]

Those six squarish black plastic things with the electrical connectors are the coil packs. We need to remove those because the spark plugs are under them. Do each one in turn. Take off the electrical connector, pressing down on the catch to release it and then pulling it off (I used a screwdriver to gently help ease the connector off). Then remove the 10mm bolt holding the coil pack down. Before pulling the coil pack out, you may want to check that there's not a load of dirt around the coil pack waiting to fall down into the engine when you pull it out. Carefully clean away any debris if necessary (using a can of compressed air to blow away any dirt is probably ideal) then pull the coil pack vertically up out of the engine :

[Image: plugs6.jpg]

Put the coil pack carefully to one side. Now we can remove the spark plug. It will probably be easier if you use the type of spark plug socket that contains a rubber insert. This grips the spark plug and makes it easy to remove the plug by simply pulling your socket out of the engine once you've unscrewed it. Some cheaper types of socket with these inserts might be a pain when it comes to inserting the plug (a bit later though), since the rubber insert can get left behind on the plug which you then have to remove separately. I used a Halfords Professional socket and had no such problem.

You will need some sort of socket bar extension because the plugs are quite deep, as you can see from the length of the coil pack (the coil pack sits on the top of the plug). You can get an idea of how deep it is from the next picture, where you can see the thread of a removed spark plug at the bottom of the socket :

[Image: plugs7.jpg]

Now we need to install the new spark plug. It is very important to do this carefully so that you don't cross-thread it. I recommend just using finger pressure to turn the socket extension and to screw the plug most of the way in like this, as shown below :

[Image: plugs8.jpg]

Once it's most of the way in, then I recommend that you use a torque wrench to tighten the spark plug to the correct torque (17.5 Nm). It is important not to over-tighten it.

Once the new plug is in, now we just need to reverse the previous procedure and insert the coil pack by pushing it back into the hole, installing the 10mm bolt to fix it down, and re-attaching the electrical connector.

Now repeat this on the remaining five plugs, replacing them one at a time.

Once you're done, the covers need re-fitting in the reverse order of removal, first the small thin "VVTi" cover, then the air box (not forgetting to re-attach the hose on the left side) and air inlet. Finally re-install the air filter, including the two clips.

Once everything is re-installed, reset the ECU. I'm not sure if the ECU reset is totally necessary, but it certainly doesn't do any harm, and should help to speed up the "re-learning" process that the ECU will go through in terms of adjusting to the new spark plugs and determining optimal air/fuel ratio etc.