Palio Engine Overhaul

[NIcoTest070]

hi all

on a new adventure ... rebuilding a 1.2 fiat palio ....
car had a issue every month would misfire on the 4th cylinder occasionally , i had no issue with changing the spark plug on the forth cylinder and going on for the next month or 2 , or for the matter even rotating the spark plug between 3rd cylinder and the forth cylinder ..., but eventually my car kept going on but the forth cylinder would just give up even after i put a brand new spark plug in it , the new spark plug would last for 5min and then the car would start to miss again but still work on the other 3 cylinders fine , in conclusion to find a solution i have stripped my engine to no avail still cannot find a problem , i suspected it was the rings but none are broken , my main concern is if i overhaul the engine and if i have the same issue there after which will be a real disappointment to me .... , i would like and appreciate any help to conquer this situation of mine

 

[UnoMia]

Hi,
Is the 4th cylinder plug becoming fouled with oil? Is the engine using any oil or does the exhaust smoke? If it's not doing any of these things then consider changing the plug leads as the starting point.