Adding IAC to the 22RE TB

The Toyota ISC (Idle Speed Control) can be removed by turning the throttle body upside down and removing the 4 attaching screws.

The Toyota ISC is sealed with rubber beads, like O rings.  The thermostatically controlled valve is referenced to coolant temperature.  The coolant passage is on the left and the two air passages are on the right. Coolant flowing through the ISC doubles as the thermostat bypass.

Here is the throttle body attaching point for the original ISC. The large passage is for coolant and the two smaller holes are for airflow.  Notice the sealing surfaces are flat which allows a gasket to be used instead of the rubber beads used by the OE.

Chrysler / Jeep 4.0l IAC housing. Simple. Attaches to throttle body with 4 screws, has passages for air in and out, and Chrysler IAC attached. Gasket exactly matches housing face.

Adapter plate and gasket. Gasket was made first as a template. Holes for coolant passage allow visual confirmation of proper alignment when IAC housing is installed. Notice holes for airflow and IAC housing attaching screws.

Adapter plate installed. You can still see the tracings from the gasket. No coolant flows through this adapter as IAC is controlled by computer. Colder TB should mean denser air into engine, too. Dedicated thermostat bypass tube must be installed in intake.

IAC housing attached to adapter plate. Different fastener in upper LH corner is due to very tight clearance after TB is installed. Button head screw might have been more appropriate.

Throttle body installed. Notice 5/16" diameter tubing used for thermostat bypass Teed into heater hose near oil filter. IAC wiring extends toward passenger side and valve is tucked neatly under throttle body.

Another shot of the installed throttle body. IAC is almost invisible from this angle. 5/16" thermostat bypass tube makes U-bend under MAP sensor and connects to same location as original coolant hose from ISC. Without this bypass you risk large temperature spikes and possibly overheating. Original wiring harness routing and air intake piping tend to hide the IAC valve. Unless you know what you're looking for, you might miss this modification altogether.
IAC Install Sequence

Toyota ISC


Jeep 4.0l IAC housing

Adapter plate and gasket

Adapter Plate Installed


IAC in vehicle

IAC installed

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