Could be too much fuel being burned. Gunk is building up, and when the engine is reved, the build-up is forced out. I have the same problem, and black spots all over the wall in my garage. Running rich sounds right. Best to get it fixed before you develop converter problems. Your fuel economy will improve dramatically. Do you have a check engine light on? If so, get the code read to you, and it's possible that you have a bad 02 sensor, I had the same thing with my 96 Explorer, replaced the 02 sensor. A few minutes after replacing the 02 sensor, I blew the rest of the carbon out of the exhaust, and havent seen it since.
black is excess fuel
No. A bad head gasket would cause water to come out the tailpipe. You will see white smoke. Leaky rings would cause oil to come out the tailpipe. You will see blue smoke.
Head gasket or cracked head
Excess fuel causes black smoke.
Need to know why this is necessary.
Black smoke usually means the engine is running too rich. The fuel/air mixture is incorrect. Blue smoke is oil burning.
White smoke is a symptom of a blown head gasket.
Blown head gasket. Or a missfire cause by a bag ignition coil, fouled plugs, too little fuel pressure, timing is off ect.
It could, depending on the cause of the misfire.
my guess would be bad piston rings
blown head gasket!
No, the engine exhaust is what comes out of the tailpipe.