Jeep GC 2001 105,000miles
There is a whistling in the engine compartment when I take my foot off the accelerator. Once the engine is turning at less than 1000RPM the whistling subsides. The noise gets worse in cold winter months. A local automotive center thought it may be the IAC (intake air chamber?) motor, cleaned it out with IAC cleaner, but did not make the noise go away. They did not know what was causing the whistling. The whistling has been going on for almost 3 years now. Sometimes it will whistle just with idling in park
IAC is Idle Air Controller. It controls idle RPM.
“When I take my foot off the accelerator” suggests to me that the whistling is occurring at a time of high vacuum. When you’re driving along and remove your foot from the accelerator, the pistons continue to try to pull in the same amount of air, but the intake path becomes obstructed by the now-closed throttle plate.
I’d guess you have an air leak somewhere in the intake ductwork. With the hood up, your head under it, and a helper managing the throttle to find the whistle spot, the source of he whistle may become obvious.
Thank you for the comments and suggestions. However, when I took it to the first garage they agreed with your 100%. The throttle plate was cleaned and scrubbed around the opening. The noise went away for a day, then came right back. Would the IAC housing cover be causing the whistle?
The second time I had it looked at was at the Jeep dealership and the jeep whistled all the way to the shop but when they brought it inside to look at the whistle ran and hid. The mechanics thought I was a little crazy since they said the IAC was fine and clean and whistle-free. :-/ So I am still at a loss.