Low Running Temperature
Here's a mystery. Since the weather turned cold my 16V seems to take an age to warm up and only reaches about 80C. Also, it doesn't appear to be revving as freely at high revs as it used to, which makes me think the plugs may be a bit sooty.
I assumed the thermostat was jammed open and bought a replacement (second-hand). This hasn't resulted in a change, except that running temperature now reads slightly lower than before.
Today, I tried testing the original thermostat the old-fashioned way in a saucepan with a thermometer. It seems to be performing correctly - starting to open at about 75 and fully open with the port to the black 'T' pipe union closed by the time the water boils.
Clearly, it isn't jammed open, so I was wrong in my original diagnosis. So, is there a problem elsewhere (maybe it's just the sender), or is this normal behaviour for a 16V? I don't monitor mileage so don't know if this has changed indicating engine running on a rich mixture. I haven't pulled the plugs to have a look at them.
There are no clues from the oil temperature guage which, typically, has never worked.