E30 Zone

I was out in the car on friday, the car was running fine. I stopped off at a shop and when I got back into the car and started up it was missing on one cylinder.

I suspected the leads, one of them came off a bit easier than it should have and wouldn't go back on. After fixing that I decided it was a good time to check the plugs and found one of them to be distroyed as shown in thepictures below.

I replaced the plugs, and left the car where it was untill today when I brought it home. when I got it here I pulled out the plugs so I could do a compression test. All the cylinders were between 9.5 and 10.5 bar, the one with the broken plug included however the new spark plug from the fourth cylinder (the one the damaged plug was in) looks as though something bad is happening. Does anyone know what's up?

In the pictures below, the plugs shown are

left: old plug from another cylinder
middle: broken plug
right: plug from cylinder 4, with tar build up on one side.






Sorry for the long post.

The car's a 316i with an M40 engine.

Oh and the car wasn't running perfectly on the way home, it wasn't smooth.

Peter

Worn valve guides or oil seals or piston rings.

thanks smithy318i.

Would the compression test have ruled out oil seals/piston rings?