This was written in 2007 by an owner changing his plugs for the first time on any car. He says it's very easy, and he took photos along the way. The thread doesn't say which engine his car had. The photos show a four-cylinder engine with a coil pack across the cam cover, which looks like the NA engine, and the 20 Nm figure below is for that. The Turbo is covered in the note on torque.
Steps
- Get the right socket first. The spark plug socket the author already owned was far too big, so he bought a new one from Halfords. The packet read 16 mm deep x 10 mm. Another owner thought it looked deeper than 16 mm, and the author replied that he thinks the 16 mm is the depth of the middle part that slots over the plug, but wasn't sure. The thread doesn't settle what the two numbers mean, so check that yours fits the plug before you start.
- Take the screws out of the top of the coil pack.
- Lift the coil pack out. You don't need to disconnect it. Just rest it in the engine bay.
- Take the plugs out with the spark plug socket and a ratchet. The author's were very hard to remove, especially the one on the far right, which showed signs of water ingress.
- Fit the new plugs by doing the same in reverse, and don't overtighten them. Use plenty of copper grease on installation.
Torque
The figure quoted from the TIS is 20 Nm, so "tightish". One owner asked whether that meant a small "ugh" rather than a full grunt, and the thread doesn't answer.
The Turbo figure is different. The torque values list gives 25 Nm for the spark plug, but that is in the Turbo engine section, and its source isn't known. In the torque values thread, one owner says Turbo plugs have crush washers, so the aim is a good seal, and that hand tight with a ratchet is probably tight enough but not over-tightened. That is an owner's view, not a figure.
Tips from other owners
- Clean the coil tips. One owner took off the four rubber parts and cleaned the tips of the coil with emery paper, because some had rust on them from water ingress.
- Loose-feeling connections. One owner found the contact between the plugs and the coil pack connectors "pretty unconvincing" and asked how to make them click properly. Nobody answered.
- Clearing debris from the wells. To clean the dirt out of the well that covers the plug, poke with a bit of wire, give it a blast from an airline, and then suck it out with a vacuum cleaner. Our own suggestion, not from the thread, is to do this before you take the plug out, so that nothing falls into the cylinder.
- Engine hot or cold? One owner had his done at a garage, with the plugs changed as the first thing in a service, only 10 minutes after the car was fully hot. The plugs were too hot to hold for more than 2 seconds. He had since read elsewhere that the engine should be cold, below 40°C at most, before changing plugs, and wondered whether fitting cold plugs into a contracting aluminium engine could be catastrophic. In 2013 another owner, whose plugs were very rusty from serious water ingress, asked whether it is better to remove old plugs hot or cold. One reply: if you're worried about cold plugs you can warm them up before fitting, and he personally fits plugs when the engine is cold or lukewarm. Another: removal is only a problem if they were put in too tight. The thread gives no definitive answer.
- Rusted-in plugs. One owner got the engine up to temperature and sprayed penetrating oil in every other day for a week before trying to remove his. The thread doesn't say how it went.
- Choice of plugs. Owners fitted NGK platinum plugs (one in a supercharged Z22SE with no problems) and NGK laser platinum. These are owners' choices, not a recommendation, and the thread doesn't say which plugs the factory fits.