The spark plug replacement on a 4th generation Toyota 4Runner is a job that you will need set aside 2-3 hours for. The replacement of the spark plugs themselves doesn’t take long, but most of the time will be spent removing components in the engine bay to get access to the spark plugs. I recommend using a step stool to get some additional height as you will be working closer to the middle and back of the engine bay; this is especially needed if you have a 4Runner that has a lift on it. This guide is written for the 4.0L V6 (1GRE-FE engine code) on the 4th Generation Toyota 4Runner.