How to find which cylinder is misfiring
Two counters and one swap answer the question a garage charges money for.
Warm the engine up and open the misfire counters
On a cold engine even a healthy car misfires: the mixture is rich and the plug works harder. Wait for operating temperature and look at the per-cylinder misfire counters — they count separately for each.
See whether one counter ticks or all of them
This is the key distinction and it halves the search. ONE ticking means that cylinder: plug, coil, injector, compression. ALL of them ticking a little means a shared cause: fuel, pressure, an air leak — and the cylinders have nothing to do with it.
Swap the coil with a neighbouring cylinder
The most honest experiment in all of diagnostics, and it is free. Take the coil off the suspect cylinder and fit it to a neighbour, and its coil to the first. Clear the codes, drive for a few minutes and look at the counters again. ⚠️ Switch the engine off and let it cool first: the coil sits in the plug well and can be hot.
Read the answer
If the misfire MOVED with the coil, the coil is at fault. If it stayed on the same cylinder, the coil is innocent and the plug is next: swap it the same way. If nothing moved after the plug either, the injector and compression remain — and that is a conversation with a mechanic.
Do not put it off if the light was flashing
⚠️ A flashing light means misfires happening now, and unburnt fuel melts the catalyst in minutes. Do the swap in a car park, not «on the way, while we are at it».