The engine is getting more fuel than your ingnition system can light causing raw fuel to be dumped into the exhaust.I would suggest you have a mechanic check for fuel injectors staying open,if that is not the problem have an analysis done on your ignition system to check primarily your spark.Make sure you get your vehicle checked as soon as possible,this is extremly dangerous.
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
no but it may cause it to stall if exhaust is blocked
black is excess fuel
May be a bad fuel pressure regulator.
Excess fuel causes black smoke.
Often that can be the result of a sticking injector that puts too much fuel into the engine. The fuel will eventually burn somewhere, and that may be when it comes out the exhaust.
If you have sparks coming out of this pipe call a licensed electrician or your local building inspector right away.
White smoke is a symptom of a blown head gasket.
It could sink. (The metal's density is greater than water.) It could turn into a ball of flames. (If you dropped a chunk of sodium into graduated cylinder, it would react with flames or sparks.)
engine coolant getting into an engine cylinder from a bad head gasket , cracked or warped head
bad plug wire