When an engine severely overheats a valve or valves can "tulip". This condition can cause the valve to seat lower in the valve seat causing the valve to appear higher than normal. Time for the head to be rebuilt.
There is likely a crack in the engine block.
That cylinder is burning oil, from a bad valve, or worn rings, most likely.
Most likely it's a faulty ignition cylinder.
cracked cylinder head
likely the egr valve and /or sensor is bad
It will likely cause you to pass out resulting in extreme injury.
Homoygotes for one allele are favored over all others.
Most likely a bad coil (each cylinder has one) located at the top of each spark plug
Most likely a bad ignition oil. Each cylinder has its own coil mounted at the top of the spark plug
Homozygotes for one allele are favored over all others.
If it's just the no. 2, most likely cause would be a bad fuel injector (for EFI engines).
While an incorrect fuel/air ratio can cause a misfire, it's not likely to cause only one cylinder to misfire unless you have tuned port injection. The more likely cause is the ignition system... Distributor cap, rotor, plug wires, or spark plugs.