I recently found an old 8-year-old film Nikon SLR that I used. There was a roll of film in it for 3-4 years. So I finished taking photos with the whole roll and when they were developed, most of them were totally white.
There was also a problem with autofocus. It always focused a few feet in front of the subject, so I manually focused all the photos. What do you think it was caused by? Should I check if the mirror is flipping or if the shutter is working or could it be due to some other problem?
I don't think there is any problem with the light meter or exposure meter since I also took a few photos in manual. I am a photography enthusiast and usually use a Sony dSLR.
Most likely the battery is near death or has died. These cameras require a good battery to operate the exposure meter and focusing mechanism. As to the “white” pictures; old film is unpredictable as film is a perishable. Examine the film, not the prints. Film has imprinted on it frame numbers, emulsion numbers and batch numbers. These you will find on both edges of the developed film. This edge printing is applied during manufacture. The numbers, letters and other patterns are exposed on the film by means of a light projector. Because edge printing is exposed via light, the presence and intensity of the edge printing can be used to check the correctness of the film processing.
I advise, clean up the camera. This includes replacing the battery. While you’re at it, burnish the battery compartment contacts using a pencil eraser. Good clean battery contacts and a fresh battery will likely remedy your problems. If the edge printing is bold, likely the film’s age and processing technique are not to blame. After cleaning and battery replacement, try a fresh roll of film and shoot and process a test roll. Best of luck!
Most likely the battery was no good, which caused the automatic mechanisms in the camera to not work correctly. You said this camera hasn't been use for 3-4 years, and you apparently don't know how fresh the battery was even then. A battery check, or just replacement without checking, should have been the first thing you did.
There is a possibility that the film was abused during those 3-4 years. To distinguish that from bad exposure, compare the image areas to the sprocket areas. If the sprocket area of the film is unexposed and the frames are clearly visible, then the pictures were overexposed. If the whole film is exposed, then the film went bad or there was a massive light leak somewhere. However, a light leak, even a bad one for a long time, would leave splotches and not expose the whole film. Several layers of unexposed film are quote opaque.
Your question doesn't give us a lot to go on without an example image.
In addition to the other answers regarding battery life, it may be that your camera has a small light leak that, over time, causes the film inside to be overexposed.
If you use a fresh roll of film, shoot it fairly quickly, and then remove it from the camera shortly after you exposed it you can compare those results to the film that was inside the camera for an extended period of time. If you have a light leak it will only show in certain areas if the film that will give you clues as to where the camera is letting the light in. If the results are the same as before then you know there is something else going on, most likely with the light meter. You can test that by shooting part of the test roll manually in known light with settings known to be correct for that light (i.e. f/16 at 1/100 second with ISO 100 film when in bright sunlight).