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
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
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
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
looking for, you might miss this modification altogether.