Car is a SKODA  2006 Fabia Ambient 16 valve, The car is prone to intermitent  missfiring when idling, It has just had the coils and spark plugs repalced. I have purchased a Diagnostic reader and it shows that the missifie sometimes occurs on cylinder 1 and other times on cylinder 2 or 3.  Ween i erase the code it runs sometimes for several days before this problem reoccures, and it only happens when the car is idling. Can anyone give me any indication of where the fault may be, i would appreciate comments from the vast knowledge on this site

Do you have the fault code number(s) rather than just cylinder ids? Most of the ignition faults I know don't migrate between cylinders (or at least will only occur on {2 or 3} or {1 or 4}).

Does it only happen after the engine is fully warmed up?

 

I'm wondering if the thermostat in the airbox/engine cover has failed, leading to only hot air being supplied to the engine.

 

Ideally get someone with VCDS to look at the temperature of the intake air as measured by the combined MAP/intake air temp sensor.

EGR valve may be clogged up or sticking.