Do it yourself, change the ignition coils on your Volvo XC90. You will require T25 and T30 torx bit drivers and a 10 mm socket. The replacement is not that difficult, but it will most probably take you more than half an hour. The ignition coils on this car are located beneath the plastic engine cover. You will have to remove that cover, to gain access to them. So, after you lift the hood of your car, you can start by removing the two T25 torx screws that hold the intake tube above the engine. After you do it, use the T30 torx driver and loosen the eight screws that secure the engine cover, seen in the image below. They should come out without much effort. After you do it, lift up and remove the cover. You will probably need to take out the oil cap, as well. At this point you can access the coils. In order to remove a coil, you will have to loosen the 10 mm bolt that holds it and unplug the harness that powers it (see next picture). You can repeat the process for all the coils, install the replacements, plug back their harnesses and secure them with the bolts. In the end, reinstall the engine cover and tighen the screws of the intake hose above. This is all you need to do, if you wish to remove and replace the ignition coils on your Volvo XC90.