Where Is the IAT Sensor on a 98 F150?

On the 1998 Ford F-150, the intake air temperature sensor detects the temperature of the outside air as it comes into the trucks combustion chamber. As the temperature becomes higher or lower, the resistance in the switch lowers and rises, respectively, resulting in the powertrain control module adjusting the ignition timing and the air/fuel mixture. When this thermistor, or thermal resistor, fails, you may experience a rough idle, poor fuel economy or a slew of other symptoms. Locating, testing and replacing the IAT sensor on all three engines offered on the 1998 F-150 is the same straightforward process.

Instructions

Open the F-150s hood and find the air filter box on the drivers side of the engine compartment.

Trace the air filter box toward the passengers side until you reach the plastic tube that connects it to the engine. This tube is the air filter outlet tube.

Trace the air filter outlet tube until you find an electrical component pressed into it. That is the IAT sensor.

Check that the outside temperature is at least 50 degrees Fahrenheit. If the outside temperature is below this mark, you cannot test the IAT sensor.

Start the F-150s engine and allow it to run until the truck reaches operating temperature about halfway up the temperature gauge. Shut the engine off. Press and hold the unlocking button on the IAT sensors wiring harness, and unplug the harness from the sensor.

Start the engine and hold its rpm at about 2,000 for two minutes. Allow the engine to idle.

Set a multimeter to measure ohms and touch the two probes to the pins inside of the IAT sensors receptacle. Compare the resistance to the chart in the Tips section, using the outside temperature as your guide.

Replace the IAT sensor, if the resistance is not within specifications listed in step 5. If the ohms are within the specification listed in step 5, there is a fault other than the IAT sensor. Repair that fault and retest the system.

Press and hold the unlocking button on the IAT sensors wiring harness, and unplug the harness from the sensor.

Pull the IAT sensor from the air filter outlet tube with a slight twisting motion to remove it.

Align the new IAT sensor with the hole in the air filter outlet tube and press the sensor into the hole until its flange seats on the air filter outlet tube.

Plug the wiring harness into the IAT sensor.