I have a Pixma MX922 that's a little over 2 years old. It was printing fine, then I ran out of colored ink. I had to go a little bit before I could afford to get new ink ($50+ bucks? Really?), but I left the old cartridges in. I have since replaced them, but now when it prints, I get alternating bars of regular and faded print. If I print in grayscale, the bars are close together. If I print in color, they're further apart. They seem to only affect the PGBK cartridge, as the colored lines print normally. I have tried using a different cartridge, running an alignment, and cleaning the encoding strip, and the printer says the cartridges don't need a cleaning.
