I don't have a I3, but when my extruder was clicking, it's because my nozzle was jammed. It happen because I was printing over 240 deg C, the Teflon (PTFE) tube inside the extruder expanded. After 5 minutes of printing, the retracting distance pulled too much melted filament into the Teflon tube and jammed everything up. I replaced the Teflon tube and print at 240 deg C now; no problems.