1995 Ford Escort No temperature on gauge - Needle doesn't l

Engine Cooling problem
1995 Ford Escort 4 cyl Two Wheel Drive Manual 90K miles

Hi there,
The temperature gauge on my dashboard doesn't register anything, the needle pointer never lifts off the lower limit pin. The car runs fine, but splutters after about 20 minutes of driving and after about 30 minutes of driving starts to resemble a kangaroo.

The previous owner told me that the thermostat was replaced a couple of years ago, but more importantly there was previously a loose connection between the temperature sensor and the engine management system.

I plan to replace the thermostat again and get the sensor wired back up again, but am I right in thinking the spluttering after a while may be related as the engine management system would be delivering incorrect air/fuel mix as it would be optimised for a cold engine throughout the entire journey? E.G. Choke on full?

I am waiting for my Hayes manual to arrive so I can trace the sensor cable into the management system, but does anyone know if this is a common problem or roughly where to look for a bad connection?