Nothing at all has gone wrong with this 4Runner. It was in pristine condition when bought, and it has remained in this condition. It drives like a new car, and it never stops.
The only complaint is that the rear window does put a high load on the battery to wind it up and down when the engine isn't running, particularly if you are doing a lot of loading. Inside, the 4Runner is immaculate. The seats, carpets, roof upholstery, steering wheel, and dashboard are all in immaculate condition, without the slightest sign of wear. The only problem inside is the "jacket" around the gear stick is losing some of its stitching.
Externally, the car is spotless. It has no rust, and the only fault outside is a few scratches, mainly from driving on gravel roads to work.
I work in a very hilly region of Australia, and I travel on a dirt road to my work. The 4Runner is the 4 Cylinder, 2.4L SR5 model, with fuel carby, as opposed to injected. The 5-speed manual is nice and direct. The 4 Cylinder only lacks at speeds over 100km/h. Under that, it doesn't struggle in anyway, on or off road. On the road, it is quiet, smooth and corners like it's on rails. Off road, it's dependable, stable and never stops.
Even in 2WD, the 4Runner sticks like glue to the road, without the big body roll evident in many smaller to mid-range 4X4s. In 4WD, there is nothing that can stop it, aside from maybe deep water (being petrol, without a snorkel system).
My only recommendation for the 4 Cylinder 4Runner is to run it on higher-octane petrol (regular Unleaded petrol is around 90-91 Octane; Premium Unleaded is 98-99 Octane, and only averages 1 or 2 cents dearer at the bowser). Running on Premium Unleaded, the 4Runner is unstoppable. On higher Octane petrol, it has more power, is smoother in acceleration, has much better fuel economy (250km to half a tank) and is much happier cruising on the open or semi-open roads.
The Toyota 4Runner is a masterpiece for Toyota, displaying every characteristic of strength, comfort and reliability Toyota is legendary for.