81 corolla: oily plugs and corroded distributor cap

[Limnos]

1981 Corolla, 3 TC 1800L engine. I've been having problems with the wire connectors on the distributor cap that lead to the coil and to plugs 1 & 2 corroding badly. There's blue-green crud (copper corrosion?) on the end of the wire where it plugs into the cap, and white powder in the (aluminium?) cap opening for those conectors. I checked the spark plugs and plugs 1 & 2 were driping in oil both on the sparking part of the plug and in the well where the spark plug wire boot fits around the plug. Plugs 3 and 4 are normal, and their wire connectors are in good condition.

A few more details that may or may not have bearing on this. The car is stored 6 months out of the year and only driven maybe 5,000 miles per year. The cap and wires and plugs are about 3 years old, and the actual wires look okay. Rotor looks okay. I have another car of the same year and model and it doesn't get through caps and wires like this. I haven't noticed particularly poor performance in this car, or any abnormal decrease over time. It gets about 25 mpg city which is what one might expect of a 26 year old 3 speed automatic car with 125,000 miles. This car needs about a quart of oil every 1500 miles. That's more than my other one but it doesn't seem to be an oil burner (exhaust looks OK). This car has a rubber boot covering the distributor cap, I guess to keep it dry, but I just removed it in case it was somehow holding in corrosive gases (which should have affected all the connectors, not just 1 & 2).

So my first question is which is the chicken and which is the egg? Is corrosion leading to poor sparking and reduced combustion that is somehow changing the behavior of those cylinders so that oil is getting out past the plugs instead of being burned off? Or is poor sparking due to the oil somehow inducing corrosion in the connectors? I checked the gaps on the plugs and the plugs seem okay other than being covered in dripping oil. It's been maybe two years since I last checked these plugs so the build up of oil could be gradual, and possibly characteristic of all the cylinders, but for some reason it isn't being burned off in these two the way it is in the others.

I change my own plugs. I am always careful not to crank down too hard on them - maybe 1/4 turn past finger tight (I have strong hands too). Should I tighten these two a bit more?

[Hemi3TC]

Each spark plug tube has a seal on the end. You could clean out the oil and tighen down the valve cover a little more. No more than 8 ft-lbs of torque.

Spark plugs are tightened to around 12-15 ft-lbs. You can not do the method you suggest because you do not know how much the gasket has been crushed already.

corrosion is from moisture build up I would assume. You could clean them with isopropyl alcohol or some contact cleaner. If that does not help just replace them all.

[diver9000]

Try new: Plugs, Wires, Distro Cap and Button, and a compression test, just for good measure.

[91gtssilvertop]

Corrosion like you described is usually caused by open spark plug wires. Take an ohmmeter, check each wire. Should be approx. 8000 ohms per foot of wire. You can have an open wire and still no misfire if your coil can still produce the voltage to jump that gap along with the plug and rotor gaps.
As for the oil, your tube seals are probably rock hard and need replacing along with the valve cover gasket.