Stuck open thermostat.
You run the engine till warm then look underneath and see if the pump is leaking. A faulty pump leak is very visible in Taurus/Sable.
It will always run cold so it will run inefficiently.
On a 1999 Mercury Sable : The transaxle ( transmission ) is located in the engine compartment , bolted to the engine
Replace engine cushions
Defective thermostat ... it could be WIDE open and not regulating the temperatures properly. Allowing the engine to run cold like this can do more damage than good.
go to autozone and have them run the code for free... otherwise it sounds like the TPS or ICV
In a 1998 Mercury Sable : The transaxle is the transmission on your front wheel drive Mercury Sable it is located in the engine compartment , on the drivers side , bolted to the engine
On a 2002 Mercury Sable the radiator is at the front of the engine compartment
A high performance engine will run better in the cold the vehicle is at full operating temperature. Cold air is more dense so basically its like your packing in more air into the cylinder.
Too much fuel - and all engines run rich when cold.
The 2000 Mercury Sable starter can be found on the right hand side of the engine. The starter will be near the back of the engine.
The most common reason an engine would run cold or take a long time to reach normal operating temperature is a thermostat stuck in the OPEN position or no thermostat at all.