Hook up a scan tool or code reader and see if any OBDII codes have been set. If what you are perceiving is really a misfire, you might see 1 or more codes set like P0300 (random misfire), P0301, P0302, etc. A really bad misfire would cause your check engine light to flash constantly.
Being a 3 cylinder, these engines tend to have a bit of idle vibration that some people aren't used to.
View my fuel log 2015 Mirage ES 1.2 manual: 51.3 mpg (US) ... 21.8 km/L ... 4.6 L/100 km ... 61.7 mpg (Imp)