I am rebuilding my 1972 1800. It has a B20E engine. I rebuilt the engine myself and replaced all of the components including valves, pistons, cam, injectors, sensors and wiring. Once reassembled, the engine started right up. However, I continue to have a miss on the #3 piston. I have checked the valve clearance, the fuel injector, the firing order, the spark to the plugs and have checked the electronic controller for electrical continuity. I still have the miss. When I remove the plug, it is not gasoline fouled but it is covered with a black soot.

Any suggestions?

Thanks.