How to replace the spark plugs (ignition wires and COP)

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  • OVERALL DIFFICULTY INDEX: 3/10
  • IF YOU HAVE NO TOOLS, YOU PAY $35 TO GET THEM FOR THIS JOB
  • IF YOU HAVE NO EXPERIENCE YOU SPEND 1.5 HOURS TO CARRY OUT THIS JOB
  • RISK OF HAND INJURY, SEE BELOW
BEFORE YOU START
  • Your engine should be cold for this intervention. Do not attempt to work on a hot engine.
  • Watch out when unscrewing the spark plugs, they could loosen suddenly sending your hand onto a hard or sharp surface resulting in an injury.
  • Compressed air is mandatory for old engines to clean the spark plug surroundings prior to removing it.
​It is more difficult to replace the spark plugs on old engines rather than on newer ones equipped with coil-over-plug ignition systems.
DISCLAIMER:
Our pictorials are of informative nature and do illustrate works carried out by ourselves at our own premises for our own use and satisfaction.
Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.

Spark plugs replacement on any vehicle with ignition wires or COPs

1- Start by removing all air hoses, air filter assembly, etc. to clear the area above the spark plugs.
2- Locate the spark plugs by following the ignition wires.   
3- Pull out the wire connectors. Do not pull with the wire, make sure to hold the connector itself when pulling.
4- On newer engines you need to remove the coil-on-plug COP.
5- Lift the handle up.
6- While pulling out the connector.
7- Unscrew and remove the COP if a bolt is there or else simply take it out. Go to step 9.
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8- Blow the area around the plug with compressed air to avoid that any accumulated dirt around the plug goes into the engine.
9- You need to have the right socket, a cardan joint, two extensions of different length and a good ratchet drive handle of 3/8" or 1/2".
10- Use one or more extensions until the handle can rotate freely and unscrew the plug. It will oppose some resistance at the beginning then loosen all of a sudden and rotate freely afterwards. 
   
11- Make sure your socket did go well into the plug. Do not force in case of doubt, remove it and push it in again while rotating it right and left until it moves downwards and you feel it touching the metal.
12- Place the plugs you removed in the same order than their location in the engine. Inspect them for diagnosing  the engine tuning and condition prior to throwing them away.
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13- Assuming you bought the right spark plug and checked the electrodes gap conforms to your vehicle recommendations, place the plug in the socket. Plug sockets have a rubber holder that keeps the plug in even when pointing the socket downward.
14- Rotate it BY HAND until it stops. It should turn freely. If a spark plug does not go as deep as the others, you may have started to rotate it with an angle, remove it and repeat until it works. If it doesn't, this means the plug thread could have deformed especially if someone had previously dismantled them while the engine is hot. You need to re-thread the seat (not covered by this pictorial).
15- Tighten he spark plugs with a torque wrench to 1.75 mKg for conical plugs and 2.5 mKg for washer seal plugs. if you have no indicator or no torque wrench, tighten the plug until it stops then add 1/16 of a turn for conical seats and 1/8th for washer sealed plugs.

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