Fuel injected engines can't use Choke Plates, but cold engines still need a richer fuel mix, advanced spark timing and higher idle.
So the ECT sensor was added, ECT = engine coolant temp
This is a TWO WIRE sensor, not to be confused with the 1 wire Sender used for the dashboard temp gauge.
Normal cold start without touching gas pedal
Engine starts and RPMs go up to 1,500+
Computer has opened IAC valve all the way for starting
Computer closes IAC valve to set COLD idle, about 1,100rpms
1,100 rpms is set by ECT sensor temp, colder temp higher idle, warmer temp lower idle
As engine/ECT sensor warms up idle will slowly drop to 650 on manual, 750 on automatic
If your engine is doing this then ECT sensor is fine, if it isn't then change it, under $8
If ECT is telling the computer engine is always warm, like you just stopped at the store and restarted engine, then it would run poorly until it actually warmed up
On lima 4cyl it is usually on the drivers side front, below intake