Auto-save only works occasionally

When I first upgraded to 2.3 the auto-save feature worked fine. Then I played around with the time/date code in my K2 theloop.php to add the posting time to my metadata. Since then it appears to only work occasionally. Today it didn’t begin auto-saving until I had been writing for an hour or so. I’m unfamiliar with the auto-save code and its functioning, so am not sure how to begin solving this issue. Anyone know the answer?