94 GT oil fouled plug

Well, our PCV setup is known for sucking oil into the intake. There are relatively inexpensive oil-catching kits out there. But, I could do a compression and leakdown test first. See how the numbers look and try to rule out a problem with the bottom end. How many miles are on the motor? Depending on the condition of the engine, the valve guides may be worn and the seals may be leaking.

Well, a good test of that would be to remove the upper intake and inspect the runners for oil. If the runner feeding the cylinder with the bad plug is black/oily, you may have your culprit. It doesn't completely rule out everything else though. If you have blow by causing excessive crankcase pressure, it may be spitting excess oil through the PCV. If the motor runs well, I would probably just bandaid that issue with an oil catch in the PCV line.

The funny idle might be an electronic issue, so start checking things like the IAC and the TPS.