I changed the spark plugs today on my '07 base Vibe (here are the old plugs for kicks) and I ended up breaking off a piece from one of the spark plug caps:
I was able to re-install it just fine and the car still starts and runs as normal, but I'm not sure if that broken section may cause problems in the future or something.
Also, when I removed the spark plug from the #3 cylinder, I noticed a bit of oil on the body of the spark plug, maybe like a drop's worth. I looked down into the spark plug hole and noticed just a tad bit of brown, but nothing that looked vastly different than the other holes. Is this a major problem that I should be investigating further? What could be causing this?