Start up routine for ECC(computer) is fairly straight forward.
When key is turned on EEC gets power
It then powers 3 startup sensors and checks return voltage.
ECT(engine coolant temp) gets 5volts
IAT(intake air temp) gets 5volts
TPS(throttle position sensor) gets 5volts
ECT is a TWO WIRE sensor, only used by the EEC.
FYI, there is a 1 wire sender used for the dashboard temp gauge that looks similar.
The ECT sensor data(cold or warm) will cause the EEC to run engine rich with high idle(choke mode) if cold, or normal lean mix with low idle if warmed up.
This sensor can be tested with ohm meter, High ohms cold, ohms drop as ECT sensor warms up.
Volt meter connected to the two wires hooked up to ECT and key on, voltage will go down as ECT sensor warms up, 3volts at about 70degF, .5volts at 200degF(operating temp)
Without correct ECT sensor data the EEC will run in "Limp mode", CEL(check engine light) should come on if ECT data doesn't change or is out of range.
So ECT sensor is very important, it is the main sensor to set EEC in correct mode for startup and running.
IAT sensor data causes slightly rich/lean mixes based on outside air temp, cooler air is denser than warmer air so requires more fuel to be added, it is similar to O2 sensor in that it can cause EEC to run engine too rich or too lean if it is reporting the wrong data to EEC, so if MPG drops(rich) or engine is pinging(lean) then IAT(or O2) could be the issue.
IAT sensor can be tested the same way as the ECT sensor and will have similar ohm and voltage readings with cold and warm air.
TPS sensor gets the 5volts and if throttle is closed EEC sees .6-.9volts return voltage.
EEC "learns" TPS voltage so there are no exact voltages, under 1 volt closed and above 4.5 volts Wide Open are the specs to check.
But more important is the stability of the voltage when opening and closing the throttle, voltage should increase steadily as throttle is opened, no jumping around, and decease steadily as throttle is closed.
If there is a "dead spot" or "short spot" on the TPS then EEC thinks you have taken your foot off the gas pedal or you have "Floored it" when you hit that position on the TPS, since throttle plate position hasn't really changed engine doesn't die or run up to high RPMs but the fuel mix does change, leaning out or gets richer, so change in performance is noticeable at that problem spot on TPS.
Cold idle should be 1,000rpms +, colder outside temp = higher than 1,000rpm, but 1,000rpm would be minimum cold engine start idle.
It will then drop gradually over the first 5-10minutes to 700-800rpms as engine warms up.
If this isn't happening then either the IAC valve is not getting signal from EEC or EEC is not sending the correct signal to IAC valve, this could be because ECT sensor is reporting the wrong temp to EEC.