How to Change Spark Plugs on a Lexus Is300

The 1st gen is300 engine is a bit clutter because of its short engine bay. You will need to remove and unmount some parts to gain access to the plugs. Here is a DIY guide of the procedure described here, be prepared because there will be some risk.


  1. Image titled Enginecover
    Remove the engine cover there are 4 bolts holding the cover.
  2. Image titled Timingbeltcover
    Remove the timing cover belt. (4) 5mm allen screws are holding it down.
  3. Image titled Intakeremove
    Remove the intake tube. There will be 2 hose clamp it will be a 10mm bolt (mine has 2 if yours is stock you will have the on the top), loosen it. There will be a hose attached to the top tube by squeezing the clamp with your fingers wiggle it back and forth to get it off by pulling up towards the car. Pull the top of intake tube towards the left and it should come of fairly easy and the bottom pull upwards towards the car and it should come out. If it doesn’t come off easily unbolt the filter box and it should come off much easier.
  4. Image titled Plug3
    Image titled Plug2
    Image titled Plug1
    Review what you see. There will be three connectors attached to the throttle body (1) above, left and bottom of the throttle body). The accelerator pedal position, throttle position sensor, throttle motor controller.
  5. Image titled Throttlecable
    Remove the throttle cable. Rotate the throttle by hand so there will be a large amount of slack to the cable and remove it from the throttle body.
  6. Image titled Throttlemount
    Use 2 14mm wrench to remove the cable from the cable support mount. Loosen the driver side or passenger side and pull up to remove it.
  7. Image titled Wirebracket
    Remove engine wire bracket. There are (5) 12mm nuts attached to the throttle body and engine. 2 will be under the throttle body behind the wire. Snap the nuts to loosen as these will be on tight.
  8. Image titled Topthrottlebolt
    Remove the top 2 bolts on the throttle body. These are (2) 12mm bolts
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    Check that the throttle body is free from the engine. There is a coolant hose attached to the throttle body. The hose shouldn’t be removed unless you intend on changing your coolant and bleeding the system. You can remove the hose if you want to; doing this will give you more room to work with. If you have removed the hose you should be able to slide the throttle body to the passenger side of the car.
  10. Image titled Throttlegasket
    Remove the throttle body gasket. There are (3) 12mm bolts holding on the gasket. Two are easy to get on the top and the third is positioned 7’0 clock on the gasket.
  11. Image titled Engineharness
    Disconnect the engine harness. There are 3 harnesses attached to each coil. Push the tab and pull up, try not to pull on the wire while removing. If it comes difficult to remove use something soft to pry it loose.
    • You will have access to (2) 10mm bolts holding the wire guide. Lift and move the harness wire away from the spark plug channel.
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    Remove plug wires and coil pack. There will be 3 plugs wire on each plug that can be removed easily by pulling upwards. When removing the plug wires keep them in the relative position. There are (3) 10mm bolts holding each coil pack using an extension or a wobble joint and remove each coil. Again keep them in their relative position.
  13. 13
    Check that you can see 6 spark plugs. Usually there will be a ton of road dust and debris in the channel. If desired, you can vacuum so dirt and other things won’t get into the engine. Remove each plug using a spark plug socket; the one closest to the fire will need a wobble head to get it out.
  14. 14
    Install new plugs. Very carefully lower the plug attached to the socket into the hole. Do not drop it in you do not want to bend the gap between the electrodes. Once it has been seated tighten by hand be careful not to cross thread the plug, if it starts to get tight before 4 revolution back it out and try again. It should feel smooth all the way. You should be able to get 8 revolutions before you start to use the ratchet. Torque to 13ftlb.
    • Installation is the reverse order.


  • Use a torque wrench to tighten the spark plugs you do not want to over tighten the plugs
  • Before removing the spark plugs there will be dirty or debris in the channel. Use compresses air or a vacuum to clean the area.
  • You do not need to adjust the gap on the plug, they will be pre gap from manufacture
  • Use spark plug socket and not a regular socket. Spark plug socket has a rubber inside the socket to hold the plug in place.


  • Allow the engine to cool down, the engine area can be fairly hot and it will make it much easier to work on a cool engine.
  • Wear safety glasses

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Categories: Cars