Thanks Spook, I always read your posts even though they are mainly for the 940 too.

I was able to determine the cause of my carbon build up, it was slight intake gasket leak. The bolts that hold the manifold were torquing to specs, but thru the heat cycles would pull out. The fine threads used on the white blocks, combine that with the aluminum, most bolts holes may only have a life span of 3-4 times to torque, then things get loose. And will not tolerate any over torque. Because the manifold bolts do not require much torque, a dirty bolt hole my be enough spec the bolt, then the heat cycle eventually pulls it out.

When I discovered this, it was because of an unrelated problem with the oil separator, I had to remove the bulbous part of the intake manifold to access the separator, the the gasketed part still attached to the head, on a lark, I put a torque wrench on the bolts, 6 of them were loose. Helicoiled all of them then my problem went away. And this was after my valve problem. If only I had taken care of my oil leak sooner.

Now for some reason, which I never have found a satisfactory answer, is that a slight intake manifold leak, one that does not affect the idle, should cause an engine to run lean, but for some reason, the computer adds more fuel, so a normally functioning cylinder will be running richer and the leaking cylinder running lean. My intake leak was at cylinder 1, 2 and 3, my carbon build up was at 5 and 6, with 5 having the clump of carbon fall off, number 6 was ready to go at any moment.


Thanks again, it is always pleasure. Happy Holidays!

DanR
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DanR