I've got an Epson inkjet printer. When I am printing in black, the print job comes out fuzzy every couple inches. If I'm printing text, I might get 10 crisp lines, then 4 that are noticeably fuzzy. Then 10 more crisp lines, followed by 4 more fuzzy ones.

The ink cartridge has been routinely changed, and I've also repeatedly cleaned the print heads... nonetheless, the issue persists. It doesn't happen with colors, only black.

What causes this, and is there any thing I can do short of getting it professionally repaired, or replacing it?

Example: (I have no idea why FT is taking this portrait image and rotating it)