Misfiring in my experience

In my case it meant the cilinders were scrapping against the block with zero lube

Imminent catastrophic failure.

It can mean a misfire too.

I had an old accord that basically lost a cylinder (blew a valve or something) but could still drive down the road with check engine blinking because that cylinder was “misfiring.”

It happened far away from home too. I drove several dozen miles with my unintentional 3 cylinder swap.

Typically it’ll happen when your engine misfires due to an ignition coil crapping out. So the engine is now firing on only 3 cylinders if it’s a 4cyl