Got a 86 bird.and a 89 and another 86 and a 85 sports coupe.all v6 tpi cars.Heres what I understand.Theres a coolant temp senser and a coolant temp sender.the sender is a single green wire that sends a signal to the gauge cluster.the senser is up higher close to the coldstart injector.It sends a signal to the ecm.corect me if im wrong.It has a yellow and black wire coming from it. repair manual elect. diagrams show the sender for the 2.8.But the sender isnt in the cooling one or any other.now it shows the senser for the 3.1 sending a signal to the ecm.why not the 2.8? Whats happening with one of these cars is a bunch of fuel is getting into the oil.I know it could be the fuel regulator,injectors or maybe even a falty temp senser.This car looks pretty stock.dose this senser contole the fan cooling?It dosn't show it having anything to do with the fan in the wiring diagrams.dose it affect the fuel delivery in any way.I dont see how by these diagrams.Haynes Repair Manual 1982-1992 firebird.I'm also working on getting my light working on my other 86.Gota change out the sender as it is a 3.1 block swap a still got the 3.1 sender in it.

 

Depending on the year, the ECM controls the fan and relies on the CTS to tell it what the engine temp is so it can turn fan
on at the programmed temp.
Also if the CTS is not working properly ( any codes showing ?) or sending wrong info , ECM may think engine is colder
than it actually is and make it run rich full time
read
http://www.chevythunder.com/cts_diagnostic_pg2.htm

$14 for a new CTS