Today my rebel xs was overexposing outside pics in auto mod. To get some kind of shot I have to go to manual with shutter at 1/4000, aperture 36, iso400 and still am getting heavy overexposure. Why?

You need to understand the relationship and teractivity of aperture, shutter speed and iso. In Av mod, you choose the aperture and the camera makes thw shutter speed agjustment, In Tv mode, you set the shutter speed and the camera makes the aperture adjustment, In manual, you have to set both shutter speed and aperture manually. If the ISO mode is set to AUTO, the camera chooses the sensors sensitivity to light automatically. Change to specific ISO
(200-400 for daylight and 799-1600 for night). Take a picture in AV mode and note what shutter speed the camera chose. Then switch to TC mode choose the same shutter speed and see if camera chose the same aperture(f-stop) you chose in first shot. Change to Manual and choose same f-stop and shutter speed the camera chose for you in the other modes. Compare all three photos. They should be almost if not exactly the same exposure wise.
In Tv mode choose a dlowers shutter speed, In Manual choose a combo of slower shuuter and wider f-stop(smaller number). Read your manual.

If your camera is a Rebel XS you should have a dial on the top right with a series of letters and icons. To set your camera so you manually control the shutter speed turn this dial too "TV" (Time Value). This setting will allow you to select the shutter speed and the aperture will open or close to achieve the correct exposure. The "M" is (Manual) where you would select both the shutter speed and aperture "AV" is (Aperture Value) where the user selects the aperture they want and the shutter speed increases or decreases to obtain a proper exposure. The "P" (Program) mode allows the camera to automatically select the shutter speed and aperture

Its exposure problem you need to take canon service center and tell them to adjust exposure and shutter speed.

Auto Focus does not determine exposure. Only sharpness. "Wrong" exposure could be due to the metering mode being set in Spot Metering. Set it back to Evaluative Metering which may improve the overall even exposure of your shots. Test your shots in full auto or P mode. M (Manual) mode will require you to check the exposure setting manually (you can see the indicator in the viewfinder when you half-press the trigger)

There is an action shot setting on the wheel on the top of the camera. If you want to manually control the camera:
-Raise ISO -Select Tv mode (shutter priority mode) -Select a fast shutter speed -Manual focus on what you want to take -Take multiple pictures so one will be good

Suggestion.... try to reset all settings to default. See what happens then.

You are massively overexposing the picture. Manual mode means you have to set the exposure manually. You need to adjust the settings so that the light meter reads somewhere around the zero mark.

M mode is most useful for flash photography where you want a certain level of ambient illumination in the picture as well.

If you want some control over the camera but don't want to worry about exposure too much, use A and S modes. The manual will explain all of these modes.

You may try this. Reset all in the menu setup.
What you will be doing to to reset all the settings back to factory settings. Then you will want to go through the settings and reset them the way you prefer.

You didn't mention whether your Rebel was a film version or digital, but as best I can see from the manuals they are quite similar with regards to your question.

The camera does have a light metering function, but you won't see a needle like some of the older film cameras had. Instead, you will see in the viewfinder the shutter speed and the aperture settings. For example, 500 4.5 would indicate that the camera has determined that the shutter speed will be 1/500th of a second and the aperture f/4.5 to properly expose the shot. Depending on what mode you are in, you can control one or both of these numbers. If either number (or both) are flashing, it indicates that the shot will be overexposed or underexposed, and you must take some type of corrective action that the camera cannot do itself with the current mode settings.

Canon has manuals available online for all the digital Rebels and many of the film Rebels. See this link. Select EOS (SLR) Camera Systems in the top box, and choose the appropriate categories in the next two boxes, then click Go.

Action shots generally require a fast shutter speed -- to freeze the motion. So you need plenty of light or a "fast" lens. A fast lens is one in which the aperture opens further to let in more of light. The smaller the number of the maximum aperture, the faster the lens, so a 28-105mm f/3.5-4.5 lens is "faster" than a 28-105mm f/4.0-5.6 lens. But usually, faster lenses cost more.

For the settings on the camera, the Rebel K2 has a Sports image mode (silhouette of a runner) on the control dial which should get you appropriate settings for most action shots.

If you want to set the shutter speed yourself use the Tv mode, and with a fixed shutter speed, the camera will set the correct aperture. Watch in the viewfinder -- if the aperture value is flashing, it means the shot will be underexposed. You will have to select a slower shutter speed.

Another way to get action shots with limited light or a "slower" lens is to use film with higher ISO/ASA. ISO 100 film is good for daylight shots, but for inside shots or evening shots, use ISO 400 film. Higher ISO film is "grainier", so enlargements will show less detail.