If anyone still needs information on how to change the spark plugs on a 998cc IQ, I’ve provided details below after completing the job this afternoon. It should take about 90 minutes and is pretty straightforward.
Tools required: 10mm socket, 10mm spark plug socket and extension, cross head screwdriver, flat head screwdriver, 3 new denso iridium spark plugs
1. Disconnect the battery connections
2. Loosen the clamps on the large inlet rubber pipe (cross head screwdRiver or 10mm socket) and the clip on the small side pipe on the right hand side of this pipe - and remove
3. Disconnect the 2 electrical plugs on either side of the throttle body (which the inlet pipe goes into. To do this you willl need to press down the clip on side of the connector and ease it off. A flat head screwdriver can help to press down the tab and ease the plug off. It may be useful to disconnect the clamp which holds the wires, by pressing on either side on the tabs where the connector mounts.
4. There are 4 bolts / nuts holding the throttle body in place. Remove the 3 bolts on the front of the throttle body using a 10mm socket. Remove the 10mm nut on the right hand side and slide the throttle body forward. You may want to unclip the 2 rubber hoses at the top of the throttle body where they clip into rubber clips - just press upwards with your fingers to unclip
5. Slide the throttle body forward until it is just clear of the stud which the 4th nut was connected to. Then lift the throttle body up by a couple of inches and insert the stud into the mounting hole. This will keep the throttle body out of the way and ensure that the coolant hoses are not damaged
6. You will then see the 3 coil packs in front of you. Each is held in place with a 10mm bolt. Start with the first one - order isn’t important. Undo the bolt and disconnect the electrical connector. To do this pres down on the tab on top of the connector and ease off. As before, a flat head screwdriver can help here. Then pull out the coil pack and put to one side
7. Using the spark plug spanner, remove the spark plug. This takes a while as the thread on the spark plug is quite long. Screw in the new spark plug to a torque of 15ft lb. insert the coil pack attach the electrical connector and bolt down with the bolt. No torque setting here, but needs to be pretty tight. The hardest thing here is getting the socket off the spark plug - it took a bit of jiggling to get it off.
8. Repeat for the 2 other plugs. I found to get enough clearance for the middle plug, I had to take the throttle body off the stud and lift a bit higher, taking care not to put strain on coolant pipes
9. Refit the throttle body using the 3 bolts and the nut (to connect to the stud)
10. Reattach the electrical plugs on either side of the throttle body, and the connector holding the wire in place, if you removed it
11. Reattach the inlet pipe, and tighten the 2 clamps at either end and the clip holding the smaller side tube in place
12. Reconnect the battery terminals
13. Start car and congratulate yourself for saving so much money by not getting the dealer to do it for you and that it’s 60,000 miles until you have to do it again!
I hope this is useful to someone.