my car would misfire only on idling <1000 rpm after only 30 seconds. Because this is manual transmission, I could drive it all day without getting into the "mode".
For example: If I just start the car, when is cold, it would take time to heat up and as soon as rpm's get down to about 800, it would start misfiring.
If car is hot, it would start misfiring within 30 seconds.
But if I keep gas pedal pressed so rpm's are above 1000, it would never misfire, as computer wouldn't complain, and I believe that's because pressure in cylinders are much higher than while idling.
Misfire was because of the fuel cut off by computer, and that was because computer sensing slight misfire, so to protect the cats, it cuts the fuel on those cylinders. I hope this helps.