cold stalling each year,what can be wrong?

[petaling]

last yr cold stalling usually at incline or turning off ramp ,usually at minus 10 to 20 degree celsius
rest in underground heated car park.starts again
changed voltage regualtor,same thing
changed back from plat to copper though resistance plugs ,same thing
finally last yr mechanic over the phone diagnosis,change battery,went thru last yr without further stalling.This yr got new battery again one month ago as prophylaxis just in case.so battery Interstate 91 HD only 1 month old.

This yr 1st cold snap,yesterday and today minus 20 celsius,ie minus 4 fahrenheit, or 4 below F.stalled again,jumpstarted sputtered and started.
Added gas line antifreeze to already almost full tank.

checked battery,12.35 with ignition off and alarm on only.Idling,13.8 -9 V,1500 rev 14.0 or 14.1 V. With batt disconnected tonite after driving home and charging battery by alternator only ie by driving home,12.77 V (disconnected from car)

I am thinking of changing the plugs to mercedes non reistance plugs,other than that,are there anything that one may suspects,Are there any grounding points for the alternator that is easy to reach in cold weather.The groudning point for the battery negative terminal seem s okay.


bad contacts when cold,bad contacts at ecu???????Dist rotor and Bosch wires only few yrs old.

Thanks for any advice