When you take the valve cover off, there are four plug tunnels w/ rubber seals...three look like they were milled yesterday, while #4 is stained orange/yellow/brown and has a dark, dark rust-colored powdery filth in it. The #4 plug is totally black as well.

I started doing this today because I'm getting a rough idle and a slight sputtering/clicking(ping is pre-ignition, right?) during acceleration...cleaned the ICV with carb cleaner, but it just smoothed the idle by about %50...still a bit rough.

So why would #4's plug be so dirty while the others weren't?...could it be as simple as the #4's valve cover/plug tunnel seal is leaking? But wouldn't that just fill the tunnel with a little oil? Would it make the plug black and the inside of the tunnel orange?

here's a pic of #4's plug next to one of the others...thx for any help

 

next i would do a compression test on that clyinder.

a lot of things can cause that, it looks like there is a incomplete burn in that clyinder
and you might be burning oil that is getting past the rings, or leaking down from the head.

 

It might possibly be a cylinder missfire which happended to my car. My number one cylinder always had burnt plugs and the car was always running rich. Definatly do a compression test. It cant hurt.

 

start with the simple ****, check the resistance on your wires.

 

It's got soot up past the threads, all over the wrench-hex. That suggests compression leaking out thru a loose plug, or worse, a crack in the head.

 

As Jim related, it could be blow-by of combustion gases past the spark plug threads from being loose. You'll note the deposits even comtinue up into the porcelin insulation where it wasn't covered by the wire boot.
It could also be baked on oil from the combination of heat and a slow leak from the spark plug tube seals.
At the least, I'd do a compression test. And I'd take off the valve cover, clean it up and inspect for cracks and indications of a prior head repair (spark plug thread repair). I've seen thread inserts leak like this before.

P

 

You think an engine cleaner like simple green get that burnt orange oil residue off the inside of the plug tubes?

 

Raid your mom's cubbard and scoff her spray can of oven cleaner. That stuff is probably baked on and may not come off without some additional help.
Leave the old plug in there and spray away. Let it sit for awhile, rinse (don't spray)with water (you don't want this sh...t on your paint.
It might just work