I wrote the below for FCCUK, but I thought I would share it here also as a reference. It is a compilation of everything I have learned about the ICV.
By the way, I bought the Kia ICV (referred to below) from a specialist Korean spare parts supplier for RM200+ (for original Kia part. OEM version is RM170+). The ori Fiat is over RM1k, so it's a big difference in price! You might be able to find it in some Kia/Hyundai service centres also (even though I went to two big ones and both were out of stock), but they can charge over RM400, so no point.
There are a few of these Korean specialists parts shops around, but I bought mine from NF Auto in USJ (37 USJ 1/1A - not far from MLM's shop). Phone number is 016 311 3548. He carries the ori Kia part, the ori Hyundai part (same price) and the cheaper OEM part.
Hope this helps!
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CONTENTS:
- What is the ICV?
- Symptoms of a Broken/Dirty/Failing ICV
- Cleaning/Replacement Procedure
- Replacement Alternatives
- DIY Gasket
WHAT IS THE ICV?
The idle control valve (ICV), also known as the idle air speed control actuator (or similar), is an electronic device that electronically restricts airflow in response to commands from the ECU, thereby controlling the revs at which the car idles. The ECU depends on different variables to determine what speed to idle your engine at, including temperature and load (e.g. load is increased if your A/C compressor is running). A working idle control valve is critical to the smooth operation of your car whenever the engine is idling (which is a lot!).
SYMPTOMS OF A BROKEN/DIRTY/FAILING ICV
A clogged-up or mildly leaking ICV will lead to your car being unable to idle smoothly. The engine may hunt around the revs, and when warm, the revs may dip too low, causing the car to stall. A completely broken ICV will lead to you being unable to idle at all, and the only way you can drive the car without stalling is to use the throttle at all times to manually control the revs.
Other issues may cause the above symptoms, but in general, if your car is idling erratically or is outright stalling while you are stopped, chances are good that the ICV is to blame.
CLEANING/REPLACEMENT PROCEDURE
The ICV is located at the top-right corner of the engine, near the inlet manifold and at the throttle body. It is circled in red in the picture below.
You need to undo the connector by pushing down on the top part of the metal clip (the part boxed in red) and then pulling the clip away from the ICV.
Next, undo the two bolts (circled) with a Torx T30 screwdriver.
Then simply pull the entire ICV away. It is shown below:
Inspect the ICV for any signs of damage. I have had an ICV split in two on me before, which results in the car being unable to idle at all. Check that the unit feels solidly put together and is not coming away or broken at any point. If you do find any physical damage, you may be able to patch it up with epoxy or similar, but I strongly recommend that you get a replacement unit (see below for notes on sourcing a replacement).
Often an underperforming ICV can be fixed by cleaning it out. Years of airflow leads to a build of up gunk and carbon within the ICV. You can get rid of a lot of this by liberally spraying carb cleaner or WD40 through both the holes on the underside (circled below), draining the excess fluid off, and then leaving it to dry.
Cleaning it does not always solve any problems - often the only way to fix an ailing ICV is to throw it away and get a replacement.
The 20VT comes with a green gasket that sits between the ICV and the throttle body. This gasket ensures an airtight seal, which is important for smooth running of the ICV. The gasket can be seen here (the green stuff):
However, over time, this gasket gets brittle and often cracks/breaks. If your gasket is broken, I recommend removing it completely, but take care to ensure none of the pieces fall into the abyss. Pieces of broken gasket and a bare recess on the throttle body without any gasket material left:
Since replacement gaskets are almost impossible to find, you can do what I did and replace it with a DIY cardboard piece (see section below for instructions and downloadable stencil):
To refit the ICV, simply screw it back in and reattach the connector. You can test the operation of the ICV by disconnecting it while your engine is running. You should hear a marked response in sound and the engine could stall, especially if the a/c compressor is running or if the engine is warm. This will also result in a temporary error in the ECU and can be checked using the widget or Startrek.
REPLACEMENT ALTERNATIVES
The ICV as used by Fiat is a Bosch unit, with the part number 0280140553. The trouble is that Fiat charges an arm and a leg for this small part, so most people source used units when their own ICVs die.
However as with all sensors and electronic mechanical parts on our cars, I do not personally recommend buying used.
Thankfully, Kia and Hyundai (Korean car manufacturers) used this exact same ICV in many of their own cars from the mid-90s to the mid-2000s. They originally used Bosch units (identical to the ones the Coupe shipped with), but then started manufacturing their own. The part numbers for the Korean ICVs are:
3515033010 (Hyundai)
0K9A220660A (Kia)
Both are exactly the same part (just that one has a Hyundai sticker and the other has a Kia one), and are physically and electrically identical to the original Bosch ICV we use in our cars.
If you need to replace your ICV, I suggest you source one of the above Korean replacements brand new (which should be much cheaper than the Fiat-supplied equivalent) rather than buy a used Bosch/Fiat unit. Then it's just a straight swap.
BMW also used this ICV in some of their E36 models (part number: 0280140575), but I suspect the price for one of these new will be similar to the Fiat unit.
DIY GASKET
I have produced a handy PDF stencil for you to make your own DIY gasket.
1) Download this PDF file
2) Print it (ensure you tell Adobe Reader to print it "actual size" in the print settings dialog box)
3) Measure the printout to make sure it is the right size (the width should be 55mm when measured from tip to tip with the ruler running through the diagram)
4) Glue the printout to a piece of thin cardboard (cereal boxes are ideal)
5) Use a blade and cut out the stencil
You should end up with a handy homemade gasket that fits perfectly in the recess between the ICV and the throttle body:
These should be screwed on finger-tight. 
