Volvo: 98 S70 T5 rough cold start, engine core, upper cylinder

Question
QUESTION: I have a rough cold start issue that only shows up when the car has been sitting for many hours and is below freezing. (haven't had warmer weather yet)  It misfires and barely reaches idle RPM and blows grey (black) smoke.  It will not briefly hit the high idle like a normal start although it still does when the engine is warmer.  After a minute or so it runs normal.  No engine light yet and tried replacing cap and wires.  Plugs are only 1 1/2 years old as were the old cap and wires.

ANSWER: Rick,
It sounds like the valves are carboned up and the rough cold starting is due to the fuel being absorbed by that carbon making a rough idle. Go to your favorite shop and have an upper cylinder intake cleaning done. When the fuel is absorbed the mixture is not correct and that cylinder begins to "miss". Hopefully the intake system can be cleaned up with the proper chemicals and procedures.

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QUESTION: A bit more info... and a question.  If the fuel is being absorbed by carbon would it still appear to run rich by blowing the black smoke?  This morning it was colder (-15C) and it started normally.  It seems worst when between 0 and -10C.  If I start it when it's only been sitting for a few hours it starts normally even though it's cold outside (engine core temp likely still warmer).  When I thought about this more, I have noticed over the past year when it wasn't too cold that once in a while it wouldn't go into high idle when starting but still idled smoothly.  Car has 250,000km

Answer
Rick,
The black smoke would seem to indicate rick running, but you say there are no fault codes. Now I have seen MAF that have been bad not show a fault code. You might try a known good MAF. You may have a bad temp sensor if only in that range you stated is the trouble area.
Since the car has some miles are you sure that the compression on all cylinders is good. There could be a low cylinder or two causing a rough engine, more noticable when cold.