Intermittent ignition misfire cyl #3. One time it starts & runs great then another time it runs on 3 cyls. replaced the plugs & the coil overs. Pcm next maybe???
Swap parts between cylinder three and another cylinder, say cylinder 1. If the misfire moves to cylinder 1 you know that’s the part that’s cuasing the problem.
- spark plugs
- wires (where applicable)
Compression would be the next suspect after that. Cylinder leak down as well.
An o’scope (or scan tool test) of the spark and injector signals should be in the mix at some point too.
I wouldn’t swap the pcm until at least all of the above had been done.
Carbon build-up on the intake valves is a common cause of intermittent misfires with direct injection engines.
Perform a web search for the Mini misfire/carbon build-up problem and you will find a lot of information.