I replaced all spark plugs yesterday after 35K kilometers. Only the spark plug on cylinder one has a lot of ash around center electrode "looks like mushroom" and the side electrode, but where the spark jumps from center electrode is very clean. What bothers me is the presence of oil on the spark plug threads. The first few threads on the electrodes side are black, moving higher towards the spark plug gasket and shell, the oil becomes cleaner to the end of the thread, I mean really clean oil. All other plugs show normal combustion.
Why cylinder one only ? and why clean oil on threads ?
Did somebody say "compression test" ?
I always thought that a leaking FD or a leaking CSV would seep to cylinder walls and pistons, looking at the intake of M117, now I can see that such a leak would cause the fuel to set in the lower chamber of the intake and cause a hard warm start-up or running rich but fuel would not cause cylinder wash out. Only a leaking fuel injector can cause that.
I will replace fuel injector on the first cylinder and go from there.
This issue of clean oil on the spark plug thread has to be from the outside, i.e. from a spell while changing oil or before I replaced the valve covers gaskets.
Ok, Replaced injector on cylinder one. New HT leads and boots, got a good deal on BWC old stock copper leads with silicone and Beru boots. These Beru boots have 5K ohm resistance not 1K like the original. First time I use NGK BP6ES running little hotter than Bosch W8DC. Oh what a difference all this feels, I kid you not I can't hear the motor at idle.