what would happen on a 3800 if an IAT sensor went bad?

 

What is a IAT sensor?

IAC Idle air control motor (Not a sensor)
AT sensor (air temp sensor)

Any car with a MAF the AT sensor would have a small effect on how the car ran. In a car without a MAF it could have a huge effect.

 

IAT is intake air temp sensor

Part 1 -How To Test: P0113 OBD II Trouble Code (GM 3.8L)

 

guess its not. just thought it was weird the car ran better with it unplugged.

 

When you disconnect the sensor you put the computer into open loop or LHM. Open loop ignores most sensor inputs. It does not mean there is anything wrong with the IAT itself, it could be but it could be any sensor that is being ignored by LHM.

Open loop is a predefined "tune" based on very limited inputs.

Closed loop is after the car is warmed up and the PCM will now making fine adjustments to the fuel and timing based on all sensor inputs.

LHM (limp home mode) is what the car goes into when one of the sensors input is outside of the excepted range. Very similar to open loop.

Is your check engine light on?

 

no its not on.

but my alternator is making some crackling noises and not making above 13 volts so I was curious if that is messing with one or more sensors.

 

If voltage is failing below 12 volt it can cause issue. If I remember right there is a low voltage code. Now if you have a sensor that is almost out of spec then you mix in low voltage it could cause an issue. Scan tool is the only real way to check it.