Can someone please explain what role the IAT sensor plays.

 

Intake Air Sensor-- acts as a thermistor. reads air temp coming into the engine...

 

Actually, it IS a thermistor..... .

What year is your car? In the 93 speed-density models, inlet air temp is one of the two most critical inputs (MAP is the other) to allow the ECM to calculate the density of the air entering the engine. Density allows it to calculate the mass (pounds) of air entering the engine (rpm/2 x displacement x volumetric efficiency x density) and add the correct amount of fuel.

In the 94 and newer "mass air" setups, the MAF sensor is capable of directly reading mass (pounds) of air entering the engine - it measures the temperature of the air internal to the MAF meter, so IAT is not quite as important, being used (apparently) for some minor adjustments to timing.

 

Thanks Injuneer, that is what I was looking for. My car is a 94. So, you say it is used for minor adjustments to the timing, just like the MAP sensor, right? So, some characteristics of this sensor being bad might be a loss of power on bottom end, spark knock, etc. and it would probably be temperature related, right?

 

A scan tool would tell you right away whether the readings were in order. If you want to test it with a meter, there are some instructions here. See the footnote at the end of the write-up.