Another funny issue with the car which I came across recently and took me an week to find out what was wrong. Intermittent fuel pump prime failure at cold start in the morning. Received S2 CAS yesterday. Swapped and all good. But wait fuel pump doesn't prime in the morning. After a unintentional small tap in relay box cover next to TPS primed the pump. Conclusion: IGN relay faulty or intermittent failure bcoz of carbon build up inside. Swapped relay with another good one and all good. Now I have two S2 PTU and two S2 CAS. Good to have some spare. Someone may find my dilemma useful one day.
When you say "carbon buildup" are you referring to the internal contacts of the relay? Meaning that you opened it up to look at it and it looked burnt? Or just the external pins and socket of the relay and fuse/relay box? What colour and condition are they? Wet? White and powdery? Light grey powdery? Green and wet? If you are referring to oxidised contacts (pins and sockets) then consider some dielectric contact grease. If you did open the relay, have you got pics?
Not worth investigating faulty internal contacts of the relay. I have some extras. External pins and socket were clean as new.
