Canon Pixma iP90 User Manual page 193

If the problem remains after performing
Print Head Cleaning three times
Step 3
See
Step 4
Note If ruled lines are printed misaligned when printed, adjust the Print Head position.
See Aligning the Print Head
If ink tank replacement does not resolve the problem, a Print Head may be worn out. In this case, contact a Canon service
representative.
Print Head Deep Cleaning
If the problem still remains
See Replacing an Ink Tank