AC compressor starts automatically even if AC is OFF.

This is not normal for your vehicle according to specifications as stated in our database. If the A/C switch is not turned on, the compressor should not engage.

Is your A/C system manual or automatic control?

Whether manual or automatic system, the A/C compressor gets its power supply from the A/C compressor relay and there are 3 possibilities for the relay to be energised.

1. Faulty relay. It is self triggering intermittently and contacting to provide power to the compressor. Try swapping out the compressor relay with the fog light relay and see if problem goeas away.

2. A short in the grounding circuit of the compressor relay. You would need to test orange wire for shorting.

3. Faulty PCM. It is grounding the relay intermittently.

The A/C system may be low on refrigerant, this will have to be checked by a mechanic with the correct equipment. If low there will be a leak that will require attention, you cannot just add refrigerant yourself as there is an exact weight required to run the system, too much or too little and the system will shut down. As for the black smoke, this will be over rich, if your car is a carburetor model, the float level may be too high causing flooding, something that a mechanic or someone with carburetor experience needs to look at, as the adjustments are very precise.