Image quality issues can be caused by different things. Finding what may be causing the problem you first need to determine what process you are using when you see the issue. If the defect is only seen on copies that is a different issue than if you see the issue on prints.
So when you try to fix an image defect first ask yourself the following: Does it happen when you make a copy? Does it happen when you print? Now try to fix the issue. If the image quality issue only happens when you are making a copy then the problem may be with the glass that the original travels over to make the copy. Clean the scan glass on the machine if it is accessible.
If the image quality issue happens when you print then try printing an internal report from the machine like the settings or configuration report and see if the defect shows on the report. If the report is fine with no defect or error then the problem is with the original file or document. Try printing a different document from a different program.
You can look up information on the print quality issues on the online support for your machine. We break down the solutions for image quality issues that happen on copies, prints or both. Sometimes you will see image issues at a regular interval like every 1 inch or some other interval, these too are covered in the online support. Another component of image issues is whether they are horizontal or vertical lines, bands, dots, or deletions. See this quick video that addresses repeating defects. This video is for Xerox WorkCentre® 7435/7535/7830/7970i but the steps and procedures are similar on most Xerox printers.
So there are a lot of components to look for on image quality issues. Knowing these components can help you narrow down the potential cause of the image issue. Before you search for solutions online or contact support make sure you know what feature is being used when the image issue occurs, in what direction it occurs and if it is at a regular interval. Now you can solve most image issues without having to call a technician you just need the right information and the support page for your printer or multifunction device.