1999 Chevy Silverado runnning rich

The plug is black and the others are clean. I replaced the plugs, coil, wires, injector, and the problem is still there. The previous plug was black on # 4 also. Only 1 cylinder black ( rich ).

It either has a bad spark plug or a bad igniter coil, each cylinder has it's own igniter coil connected directly to the spark plug, remove the black plastic cover to get to them, this is the most common problem, in some cases, but less common a bad fuel injector or low engine compression could be the cause but I would try just replacing the spark plugs to see if it helps if not replace the coil next.

I do not have a scan tool that will give me this info. But if it was a vacuum leak at or around #4 the plug would not be black (rich). The same situation with fuel pressure. The pressure would effect all cyl. Not just one. The only plug that is black is #4. All of the others are burning clean.

No, it uses just a bit but not an abnormal amount

#2, the picture that you have of #1 is a oil control problem (rings/. Valve seals)and that is not what I am dealing with. My situation is #2, a rich condition. Thanks

My number 4 was doing the same thing on a 2000 silverado 5.3L. I pulled the vacuum tube off of the fuel regulator ( on the drivers side of the engine) and gasoline came out. The diaphram had ruptured and was sucking raw gas into the intake manifold. It repeatedly fouled plug #4 and I kept changing ignition parts. Good Luck!