cielo black smoke out with brake&batt warning lamp on

[anyaddress]

hi nice forum

any way my car is daewoo cielo 1996 1.6 dohc with automatic transmittion
the car was working fine until i have the following problem:
- when i start the car the motor starts shaking when i give more power to the motor (rpm 3 or above) a heavy black smoke going out of the exhaust and after a while i noticed that when the rpm level is above 3 and when i increase it the battery warning lamp lit on with the brake warning lamp
steps i do:
-i changed the battery to see if any difference the same problem
-i reset the ecm by disconnection battery cables(is ther is any other way)
-i checked for air leak nothing found
-i changed the spark plugs
-finally i measured the voltage across the battery when the car is on and i noticed when i increase the motor rotation the voltage increase to 16.8v dc using digital multimeter is that's normal?

any suggestion plz