Replacement plugs and COP arrived today so decided to fit the suspect COP straight away as it would be a quickish job.
Before doing so I took resistance measurements across the terminals to compare with the older ones.
Plug cap to terminals 5.3kohms
Between the terminals 0.4ohms
Took the suspect one out and checked the resistances on that ….. which were pretty much the same. Swopped it anyway. Started the engine went for a run but still the same.
Search goes on – plugs next.