Hard starting after sitting

Black smoke is too much fuel. My guess would be that there is an injector that is stuck open draining the pressurized fuel into a cylinder or several cylinders. And that is a considerable amount of fuel. And it would account for the hard start because there isn't any fuel being pumped into the other injectors until the pump builds the pressure back up.

First, increase the idle speed. Easy/cheap to do
You should idle above 1000 rpm

ecm bad..

I happened to have owned the exact Model and Year of this car. I did not have this problem but can suggest a few potential parts which can do this.

What you are describing is likely due to a "heat sink" condition in electrical components or failure of the "cold start sequence" to reset.

The cold start sequence needs a water sensor to tell the ECM to reset from driving Mode to Starting Mode. Cars usually have 2 identical sensors with 1 working the dash gauge and the other operating the signal to the ECM. This is a silent failure and usually not picked up by the onboard diagnostics. It is an inexpensive part. But, the ECM could be bad if it does not do anything with the signal. The ECM is expensive.

The other part I have in mind works the same way with the ECM. The O2 sensors also tell the ECM what to do. The cold setting for the O2 is different than the Hot setting. When the O2 is hot, it makes the engine get a signal to run lean, often too lean to start. Sometimes this error is picked up on the onboard diagnostics, but not always. Someone would need to unplug the O2 sensors and test them electrically to see what values they show.

Relays can also cause a problem like yours. After shutting off the engine relays can be hot. These hot relays will cool over time, but the points or coils inside may not work properly when the engine is restarted too soon.

Last, have your battery checked. A hot battery can drop voltage and it may be at that tipping point where electrical values are changed throughout the system.

the light means to do exactly what it says

This is just a guess, but the problem may be with the crank and/or cam sensors.

see if your engine has a ECT sensor (temp sensor that delivers information to your ECM) they are installed on the intake side of the cylinder head, it usually has 2 cables, have it checked replace if necesary

TRY PLUGS AND WIRES

Try Running A Can Of Fuel Injector Cleaner Through The Fuel. Any Auto Store Should Carry This Product For About $5.00

are you using cold temperature engine oil!
if not, try changing oil for cold temperature!

hard starting happens due to the cold temperature, air pressure is low during this season so compression inside the engine is low resulting to hard starting!

make sure that all your glow plugs are working.