Misfire 1310 & 304, 305 codes solved.

[woodngrease]

Checking the obvious first remains the best advice, too bad I often don't take it. Tried & checked everything to determine why 850 Turbo wagon started misfiring one day months ago. No vacuum leaks, replaced bad (incorrect) plugs, checked compression, coil, etc.. Then, while staring hopelessly at the poorly running engine the other day, I noticed something I had noticed many times before; thanks to the cars bad oil cap gasket the presence of engine oil on the top of the engine. I had planned to replace it eventually. I took out a rag to clean it up as usual, when I noticed how the oil had run along the top of the engine, using the gap between the plastic cover and the top of the head as a gutter, running oil right into the distributor cap. Replaced both cap and rotor, ran some gasket in a tube around edge of distributor cap before installing (to keep oil out till I replace fill cap gasket). Runs beautiful.

[cn90]

I leave the Plastic Cover in my garage.
This way I have full access to the spark plug area.
Any spilled oil can be seen right away.
The Plastic Cover is basically cosmetic.