what is an IAT?

[Aren Jay]

I see it here and there but noone says what it is.

What is an IAT?

is it the same as an IAC?

[Bradley G]

air intake temps & Idle air control

[cyclopsram]

they are not the same. Intake air temp Idle air control two different birds with similar names. Sorta like Candy and Candi, speaking of birds.

[FordNut]

Kinda like MAF and MAP.

(mass air flow and manifold absolute pressure)

[Paul T. Casey]

What is an IAT?


A little device that has caused untold ammounts of hate, discontent, and grief on a certian Marauder website, not to mention an incredible use of bandwidth.

[sailsmen]

Intake Air Temp - the temp of the air as measured by a sensor at a point in the intake. An S/C kit had the IAT before the Intercooler. A member asked if it should be after the Intercooler. Subsequently a mod was offered at no charge to add an IAT sensor after the Intercooler.

For more info do a search users Zack and JerryBarnes 11-06 to 2-07.

[captain]

Idle Air Trim
Idle Air Trim is designed to adjust the Idle Air Control (IAC) calibration to correct for wear and aging of components. When engine conditions meet the learning requirement, the strategy monitors the engine and determines the values required for ideal idle calibration. The Idle Air Trim values are stored in a table for reference. This table is used by the PCM as a correction factor when controlling idle speed. The table is stored in Keep Alive Random Access Memory (RAM) and retains the learned values even after the engine is shut off. A Diagnostic Trouble Code (DTC) is output if the Idle Air Trim has reached its learning limits.
Whenever an IAC component is replaced or cleaned or a service affecting idle is performed, it is recommended that Keep Alive RAM be cleared. This is necessary so the idle strategy does not use the previously learned Idle Air Trim values.
To clear Keep Alive RAM, refer to PCM Reset in Section 2. It is important to note that erasing DTCs with a scan tool does not reset the Idle Air Trim table.
Once Keep Alive RAM has been reset, the engine must idle for 15 minutes (actual time varies between strategies) to learn new idle air trim values. Idle quality will improve as the strategy adapts. Adaptation occurs in four separate modes. The modes are shown in the following table.


<TABLE cellSpacing=0 cellPadding=3 border=1><CAPTION>IDLE AIR TRIM LEARNING MODES </CAPTION><TBODY><TR><TH vAlign=bottom align=middle>Transmission Range </TH><TH vAlign=bottom align=middle>Air Conditioning Mode </TH></TR><TR><TD vAlign=top align=middle>NEUTRAL </TD><TD vAlign=top align=middle>A/C ON </TD></TR><TR><TD vAlign=top align=middle>NEUTRAL </TD><TD vAlign=top align=middle>A/C OFF </TD></TR><TR><TD vAlign=top align=middle>DRIVE </TD><TD vAlign=top align=middle>A/C ON </TD></TR><TR><TD vAlign=top align=middle>DRIVE </TD><TD vAlign=top align=middle>A/C OFF </TD></TR></TBODY></TABLE>
THIS IS ONLY THE TIP OF THE ICEBERG
BUT IT MIGHT HELP
TINKERING WITH SOME OF THE EFFECTED COMPONENTS WILL CHANGE ANYTHING FROM START IDLE TO FUEL MIX. AND MORE

[Aren Jay]

two IAT's?

Anyway If I have a possibly bad IAC and am considering getting a SC kit. Will replacing the IAC before I get the SC Kit be a waste of money or prudent move?

[RF Overlord]

Diabolical, all of the available S/C kits use the stock throttle body so you still need a working IAC.

[captain]

It is not "hardware" you cannot see it or touch it. it is a software strategy. It gets info from many places and things. Then it tells hardware what to do with its decision. Much of its data is collected from the IAC. Which can be tested without disassembly. Using an amp probe.
The voltage should "curve" gently across the table as you hit the gas. Replacing or removing the IAC will damage the strategy. Which will then need to be "Re educated" through the process stated above. Gleaned from the Ford repair manual.

[captain]

Intake Air Temperature Sensor
The intake air temperature (IAT) sensors (Figure 34) and integrated MAF type (Figure 37), are thermistor devices in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.
Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.
Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.
The IAT provides air temperature information to the PCM. The PCM uses the air temperature information as a correction factor in the calculation of fuel, spark and MAF.
The IAT sensor provides a quicker temperature change response time than the ECT or CHT sensor.
Supercharged vehicles use (2) IAT sensors. Both sensors are thermistor type devices and operate as described above. However, one is located before the supercharger at the air cleaner for standard OBD II/cold weather input, while a second sensor (IAT2) is located after the supercharger in the intake manifold. The IAT2 sensor located after the supercharger provides air temperature information to the PCM to control border-line spark and to help determine intercooler efficiency.
Currently two types of IAT2 sensors are used. A non-intergrated type (Figure 34) and an integrated type, which is part of the Thermal Manifold Absolute Pressure (TMAP) sensor (Figure 41). The TMAP sensor consists of a IAT thermistor and a manifold absolute pressure (MAP) sensor. The thermistor portion of the TMAP is used for IAT2 function and operates in the same manner as a non-integrated IAT2. For additional information on the MAP portion of the TMAP, refer to the Thermal Manifold Absolute Pressure Sensor description and operation found later in this Section.


file:///C:/TSO/tsocache/IBM-BEA88CBE9E1_2344/V32~us~en~file=A0009679.gif~ge n~ref.gif


Figure 34: Intake Air Temperature (IAT)