I have a 1988 jeep cherokee its idling rough smells rich in fuel and has some visible smoke coming out, looks more black when cold but sometimes more blue when warm

Black exhaust smoke means the engine is burning too much fuel. The first think you should check is your air-filter and other intake components like sensors, fuel injectors and the fuel-pressure regulator. Other reasons could be a clogged fuel return line. Black smoke is usually the easiest issue to diagnose and fix, but burning unnecessary fuel will definitely affect your fuel economy, so don't think of avoiding this one to save money, it won't work.
Any smoke coming from your car's exhaust pipe is a sign that your car is in distress. Pay attention to what it needs to ensure more miles for your vehicle.

Bad carb or fuel injection issues- the system is fuel rich (black smoke) and also fuel rich system can make the idle low. Many things can cause this but thses are just a few.

You could pay a garage to diagnose the problem cheaper than throwing more parts at it.
The problems may be connected or they may be different issues.
Yes I would change the oil and filter, but first I would make sure the fuel system is not dumping too much fuel into the cylinders.
The O2 sensor helps the computer decide on how much fuel the engine needs, along with the other sensors. And you said you have already replaced the O2 sensor.
A mechanic would take a scanner and "read" the sensors and look for something out of normal range.
The fuel pump and fuel filter are off the list as far as causing a rich mixture goes.
I would start with the rich mixture and then see if fixing that issue takes care of the no start when hot issue.
Change the oil and filter first, and see if the injector is on too much.
You can watch the spray and tell - at idle it should be very light.
Also look at the engine temp - is it warming up to normal 195 degrees? Can you tell if the fuel pressure regulator is blown and pouring fuel into the throttle body ?
Without a scanner its going to be more difficult, but not impossible to diagnose.
Let me know what you find out.

a coolant tempurature sensor will make it run to rich if it is bad. run rough at idle, and produce black smoke, engine may stall out. it also causes retarded timing, slow idle speed, cold hesitation or stumble, poor fuel milage. good-luck!! if light is on check for problem code. this will guide you in the right direction. if no scanner, any auto parts store will scan for free. repost if need be. have a good day!!

Sound like a rich by a long way; are you check if have smoke in exhaust? Black smoke is fuel, blue smoke is oil.

Also, your injectors are to big and is running rich.

Black smoke means buring rich. Have the vehicle's ECU scanned for codes and do the repair the codes describe. I'm gonna take a stab in the dark and say Mass Air Flow Sensor.(MAF)

Black smoke is a sign of too rich, or too much fuel.

Way too rich (pollution, horrible gas mileage and shortening the life of the engine by washing down the oil)...
Check carburettion.
Is this carburetted or injected?

JOAT

How about plug wires they are sometimes the problem if plugs arent getting proper fire they sure do look bad .. look for any burns and check them close

Sounds like it could be a bad map sensor.
Black smoke?