The spark plugs are situated at the sides of the cylinder heads and often to change the spark plugs a spanner in the form of a spark plug socket which is in turn connected to an angle ratchet, various extension pieces and a spark plug gap gauge which is used to check the gaps of the new spark plugs; A torque wrench is desirable for the right tightening of the spark plug. Plugs are often best bought new and gauged to the required gap and it's important to remember that not all plugs are the same and getting the right size for the engine. Before you pull out any of the spark plug, ensure that the engine has cooled in order not to melt the aluminium heads of the engine and as you wait, you can inspect the new plugs and ensure that the plunges gap is correct. This is done with the use of a proper-thickness gauge whereby the electrodes are inserted and the gap is such that the gauge slides through the electrodes with a slight drag; if the gap is not correct then the spark plug should be changed since it cannot be adjusted. Start the removal of the fuel rail cover by disconnecting the fuel rail cover tab at both side of the engine, finally for safety, the removal of spark plug wire should be done when the engine is cold, this can be done by pulling the wire except for the boot in a twisting manner. If possible, blow out the spark plug hole with compressed air and wipe away any residue, put the spark plug socket over the spark plug and unscrew it anti-clockwise. Compare the removed spark plug with other spark plugs to evaluate the engine running condition, use a little of anti-seize compound on the plug threads, then screw into the threaded hole until it feels in place that it can no longer be rotated by hand; then tighten with a torque wrench or ratchet. A short length of rubber hose can be used to thread the plug into place without harm to the threads of the plug. Do this to the next plugs and, before connecting the spark plug wire, look for any damage to the boot and the wire before twisting the boot towards the plug.