Plug Wire Question

[Mr. BILL]

My '90 300SE has a slight miss at idle. I replaced the plugs 5K ago and they looked good. I remember reading here a while back about looking under the hood in the dark.

I did so tonight and noticed some arcing. The wire from the coil is running between the thermostat housing and a little metal bracket so it touches the housing. I see a constant arc at that point. The wire has a slight cloudy mark where it touches the housing.

I also observed an intermitent, random flash in wires #1,2&3 between where thewire comes out of the valve cover and the spark plug. There are more flashes at #1.

I can't remember what this means. The PO replaced the wires about 30K ago, with what I don't know. The shop that has serviced it uses good quality parts though.

Can I simply re-rout the wire from the coil? Or does that grey cloudy mark mean The wires are shot?