are idle control valves known to rattle?
 

I have a rattle from the throttle body area or the top of the engine. It is mostly heard around 2200 rpm and mostly when coasting, when the throttle is quite closed. The noise can be "adjusted" via the throttle pedal. Since the butterfly valve has no slop the most likely cause is the ICV. The idle is steady and the valve and passage has recently been cleaned. Are they a known source of noise?

If the ICV was recently cleaned, check to make sure that it was properly torqued when re-installed. Maybe the body of the ICV is loose and slightly rattling. Otherwise, check for another intake component loose.

Thank you for the suggestion. Unfortunately the sound was there before the TB was removed and cleaned. The noise did not change after cleaning.

the ones on the earlier jettas were quite noisy, as they open and close rapidly, try lubricating it with a very light oil internally

The name of these things causes confusion.

Their purpose is to provide extra air when the injection is rich during warmup of a cold started engine. It's the modern day equivalent of a fast idle cam.

After that short period, they are inactive.

If it's activating at other times, it's defective and/or the sensor controlling it is.

Thanks everyone. I don't believe the valve is atctually activating. I should have made it clear that the noise sounds like something is loose and fluttering. It is harshest around 2200 Rpm when the ICV is inactive.

If the source of the noise is the ICV it can only be caused by the valve fluttering in the bore. It does not seem like a common problem, so I'm reluctant to buy a new valve just to check.

Is this for eGas cars? This can't be true on the cable TBs. I ask because when I had the TB on my 98 off for cleaning the only port around the throttle plate has the ICV in it. There is no idle adjustment screw for the throttle plate and it closes air tight. According to my Durametric the throttle plate is at 0 deg with my car idling at 800 rpm. The specs also show 0 deg throttle plate angle at idle rpm. The only air for combustion has to be coming through the ICV while idling. Of course I may also be FOS.