-IAT Sensor Relocation
Relocating The Intake Air Temperature Sensor

I first heard about this modification on a Jeep forum where they were discussing 'cheap fixes/mods'. People who did were claiming to get slightly better gas mileage and power. I figured it wouldn't hurt to give it a try.

On the Jeep 4.0 engine, the IAT (intake air temperature) sensor is in the intake manifold behind the throttle body. The intake manifold becomes hot because the exhaust manifold is immediately below it. Relocating the IAT sensor to the cold airbox allows it to pick up actual ambient temperature instead of the hotter air in the manifold. Another problem is that the vaccuum coming through there is highly laden with oil vapor/fumes. This causes the IAT to become blackened, oily, and give false readings. Jeep figured this out in 2004 or so and implemented it on all the new 4.0's.

First thing to do is disconnect the connector from the IAT, there is a clip holding it in.
It takes a 19mm (3/4") deep socket, or wrench to unscrew it.

When the IAT came out it was blackened and oily. I cleaned it real good with some cleaner/degreaser.

A 1/4" pipe plug will be used to fill in the hole that is left where the sensor was.

I drew a circle on the airbox lid where I was going to drill my hole for the new sensor location. I wanted to pick a spot that allowed easy access to the sensor, and out of of the way of any other tubes or cables.

Next, I unhooked all the lines going to the airbox and undid the latches to remove the top section. You will want to drill a hole that is just big enough for the sensor to screw into and make its own threads. It is about a 1/2" hole, but I recommend using a step down bit. Just to be safe I put silcone on the threads to help hold it in place and keep any possible air from leaking in.

After putting the airbox back together you will notice the original sensor wires are going to be way too short, the wires will need to be lengthened using whichever method you prefer. I am going to solder the new wires and use a good amount of heat shrink to keep moisture out. Just be sure to match up your spliced wires accordingly. I covered my newly extended wires with black wire loom.


The Results:
I am often skeptical when things are said to give you more power AND better gas mileage. I always feel like you either get one or the other, but not usually both. I did notice a slight improvement on the highway at faster speeds. Fifth gear actually had a litte more power, which was nice. I didn't notice any other power gains with regular stop-n-go street driving. And what about the gas mileage? Were their any improvements? You ask. The first time filling up the gas tank after the sensor relocation was one of the rare occasions I was actually excited about filling my gas tank. I couldn't wait see if their was any difference. And the results since then have been.... I am seeing an improvement of 1-1.5 MPG. Every little bit counts.