87 f150 302 motor, Running rough (missing, low power, gets worse as engine gets hotter) so I looked under the hood one night and saw lots of sparking and arcing (anywhere a wire touched the block, 360 degrees around the plugs 1-4, and possibly where wires crossed each other). Changed the plugs, wires, cap, & botton today. The plugs looked good except for #6 (electrode gone, ceramic cracked, gap wire melted away). The miss seemed to go away, but still low power. I checked under the hood and still see the same amount of spark, in pretty much the same locations (except for maybe the wire crossing, which I was not positive of in the beginning). Were do I go now?
Thanks
Sky

 

What did you use for wires? Did you use dielectric grease in the boots?

 

dielectric in boots, 8mm double silicone wires
Sky

 

The problem you are having is that the electrical current is meeting a lot of resistance somewhere in the system between the cap and the plugs. This could indicate rusty or oil soaked spark plug holes that are not allowing the plug to properly ground. Might try cleaning the plug threads in the heads with a battery cable brush. If the holes are rusty, also check the ground from the engine to the frame.

 

found a broken ground from the valve cover to the firewall, but it did not change the problem.
I guess I could try cleaning the holes, but wont that push crud into the cylinder?
Thanks
SKy

 

That wire grounds to the engine, you need to look at the one which grounds the engine to the frame. If the 89 uses the same ground cable as the later models, there is an intermediate ground point in the (-) battery cable where it passes along the top of the wheel well.

 

I will look for another ground.
Thanks
SKy