When I first bought my '85 (in 2002) the thermostat was stuck open.  I
had the same symptoms as you.  In fact, during the first winter, I had
to cover the radiator about 3/4 of the way up with cardboard in order
for the engine to run right but it still took forever to warm up.  The
following spring, I replaced the thermostat and all has been well, in
that regard, ever since.

BTW ... I installed the "Standard" thermostat, not the cooler one, as
that is what the engine really likes.

Mike
Houlton, Maine

Geza Polony wrote:
> Hello all,
>
> Trying to diagnose a closed-loop erratic idle, I measured the coolant temp
> in the expansion (not overflow) container, and found it to be on low side:
> 120 to 130 degrees F. at ordinary, around town, temperatures. At this temp
> the gauge rests near the bottom, on the white mark. That's how it almost
> always is when driving around town. Isn't that low?
>
> I know that "real" coolant temps should be measured at the water pump. But
> given a 20 degree difference between the container and the pump(I'm
> guessing) isn't that still on the low side?
>
> Driving home from T-Day dinner, about 50 miles on freeway, the temperature
> never got up to the white mark on the gauge, and the engine stayed in open
> loop all the way! I know that the Temp 2 sensor is good because I've
> replaced it twice in the last six months and the two I took out test good as
> well.
>
> 1984 1.9.
>
> How hot should they run?
> Would cool running affect idle?
> Anybody run the thermostats that open at higher temperatures?
> How much of a PITA to install?
>
> Thanks!
>