Misfire

[Tihol Tiholov]

G'day gents,
This morn took my '88 90 Q NG to the streets after sitting since July and it
misfired under acceleration, both under load and when just adding throttle
in neutral. The outside temp was 0 deg. C. First try it fired then died,
then kept steady idle at about 1K RPM as it does when cold. A few days
earlier it ran fine around my property during the day at warmer temps, at
least 10 deg. C. Drive to work is short, so couldn't see, if it improves
when warm. Seemed like a steady misfire under acceleration, maybe running on
4 cyl. but then in bucked irregularly when going about 50 km/h in both 3rd
and 4th gear. No CEL (or MIL) came on.
Ign. wires are less than a year old, sparklugs - can't remember, have to
check, dizzy cap a couple of year old, rotor - not sure. Multi-funct. temp
switch is maybe 3 years old.
I suspect the coolant temp sensor for the ECU, since I haven't replaced it
over the last 7 years or so since I got this car, maybe it's the even
original one. Car has occasionally died or had low idle before when cold,
-15 deg. C or so, but then quickly recovered. Would that sensor produce the
above symptoms. If yes, how do I check it and where is it located - above or
below on the flange on the head? If not, where else should I look?
This may not be important but the car has a smaller capacity battery than
OEM (put there by someone to sell a Jeep with it), it did run well with it
in 1st gear when warmer, though. DK if that'll lead to misfire.
Sorry I'm jumping the gun before looking at sparkplugs first and tracing
spark for each cyl., just miffed that this happens on the first drive in
awhile.
TIA for all ideas.
Tihol