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This DIY is for V6 Tiburon (and others Hyundai models with the same Part Number IAC) and early I4 Bêta engines equipped with this IAC Valve
Unfortunately, i don't own a 2L CVVT engine to try this mod on, but it may work.
Hope you'll like this DIY coming from France.

What is IAC ?

IAC, or Idle Air Control valve regulate idle engine speed.
Its purpose on the car is to keep the engine idle speed when stopped and when driving at idle speed (ex. traffic), and also act as an automatic choke for cold temp starting. It also acts by keeping the engine speed for a short period of time when shifting gears, to help people shift gears more easily, and to reduce CO2 emissions to let the catalytic converter clean before returning to idle (a quick change in rpms to idle creating a excessive concentration of CO for some seconds)

Where is located IAC Valve ?

The IAC Valve is located in the engine bay, on the throttle body, juste before the intake manifold and next to the intake.

What is the IAC Restrictor Plate ?

The IAC Restrictor Plate is a small plate made of plastic or metal.
This plate is mounted between the throttle body, and the IAC valve, and is drilled with small holes.
This plate and those holes allows air to pass through the IAC Valve, but this amount of air is limited by the size of the holes, which improve the throttle response and avoid engine rpm to slowly return back to idle, but by keeping always a small amout of air can lead to hard cold starts as engine need a choke.
In order to help the engine start on cold temps,the IAC valve opens completely, letting more air pass through the throttle body, that's why the engine RPM when cold climb at 2000 rpms, then close itself partially (75%) when engine is hot, to reach 750 rpm.
The cons of this mod, is that on cold temps, we totally loose this choke cycle, the car may not start easily, or may stall multiple times before starting correctly.

Why mod the IAC Valve as explained here ?

By modding your IAC Valve as explained here, we will have the same effect as the Restrictor plate, the engine rpms will drop quickly after releasing gas. The pros is that we keep the choke for cold starts, avoiding stalling, which is the most annoying thing with the Restrictor Plate.

How does it work ?

The IAC Valve have .. A VALVE. This valve is driven by an electric motor, and by 2 PWN signals coming from the ECU. It works like a Steelyard scales.
If the Signal is raised on one side of the electric motor, it will open the valve, if the signal is raised on the other side, it will close the valve. That's why we cannot just try to electrically dump the signal and adjust the motor position, the ECU needs to be flashed and the duty cycle of the IAC Table needs to be performed (just for that .. Ughhhhh)


Whay do i need to mod my IAC :

  • A power drill
  • A small wood drill bits (2mm or 3mm)
  • A scream
  • A new IAC valve gasket (or some sealant)
  • A white pen
Time needed : 45 Minutes

1/ Turn off the engine, and open the Hood.
2/ Disconnect the IAC valve and unmount it. You will find it here :

3/ Carefully take a look at the IAC valve, there is a pin which fix the position between the valve and the electric motor.

The goal is to remove this pin. To remove it, we will need a power drill. In the case of your IAC Valve is already drilled on the other side, a screwdriver can easily help to remove the pin. If not, you will need to destroy or remove carefully this pin (don't be scared, it's still reversible)

4/ Once the pin this removed, DON'T TURN OR MOVE THE ELECTRIC MOTOR FROM ITS POSITION. If it moves, just put a screwdriver than perfectly fill the hole to set the original position of the motor.

5/ Mount the IAC valve on the throttle body, connect it and start the engine. If the motor has not moved from its position, the idle speed will be normal. It's time to move it from the original position, it will close more because the motor will still receive the same signal from the ECU, but the valve will NOT have it's original position.

6/ Engine running, slightly move the IAC Valve motor side (at right) upwards, FEW DEGREES ARE ENOUGH, the rpm will drop down to 650-680 rpm, that's normal. Be careful to not move it too much upwards, IAC Valve will detect an wrong position and the valve will open, which will lead to a sudden jump up of the rpm (as if the IAC was not closed). Just go downwards with the IAC motor until the rpm drop at an normal running value. DON'T FORGET TO GIVE SOME QUICK REVS AS SOON AS YOU MOVE THE IAC MOTOR.



7/ Do a mark between the two parts of the IAC valve to fix the position. Ensure that you will not drill to close from the original hole if you want to come back at the original position.

8/ Align your marks, then drill a hole this way

9/ Put a screw through the original hole from the valve side (left), to the electric motor side new hole to fix its new position.(Be careful to not put a big screw, you may break the plastic and your IAC Valve will be dead (you will not be able to fix the position))

10/ Mount and carefully seal the IAC valve on the throttle body, then go for a ride !

To retrieve the original functionning of the IAC Valve, just remvoe your screw, turn the motor down at its original position (original hole), and put your screw in !
Sorry for my english if there is any mistakes on this post ;)

If you have any questions, please PM me :)
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