Good places to start are, of coarsewhat the code says, colour of smoke, odour of smoke, frequency of misfires, if they happen only when cold… Ect.
It can be many issues, i wont go into what it can be because i dont want to scare you. Either way i can tell you a story atleast.
A while back on my 97 crv i had quite a bit of dark smoke and a discusting un burnt gas smell come from the exhaust, i had to keep it on recirculation otherwize i would choke to death not to mention an insane ammount of misfires.
Turned out to be the ignition control module crapping out, because it finally dies and the car didnt start so i diagnosed for a few hours, replaced it, no more issues.
You could take it to a local auto shop and just have them scan
It, look up the code number at home.
Misfires can happendue to fuel loss, conpression loss, or even ignition, spark loss.
See if you can find the code, maybe it will confirm its a misfire and we can go from there.
Good luck!!
Sincerely,
John