Can someone help me out diagnosing this whistling noise?

Highlander79

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Oct 8, 2020
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I posted about this a while ago, but never got any feedback, so I figured I'd try again one more time before dealing with taking it into the shop.

Every time I start driving a cold engine, after about 5-10 minutes I get this loud whistling noise at idle throttle. It's always throttle position dependent, not speed or RPM. Then after another 10 minutes or so, it goes away completely.

I originally thought some kind of vacuum leak, but traced all vacuum lines, not finding any cracks, and even replaced a few worn vacuum boots. I also have a P1494 code that won't go away (leak detect pump pressure switch), which is what made me think vacuum leak (but it might just be the pump itself if it's not related). But the fact that it doesn't happen with a cold or completely warmed engine makes me think leak from the block or a gasket somewhere.

A few weeks prior to this starting, I did have the exhaust manifold replaced in the shop, which obviously means removing the intake manifold, etc, so maybe something involved with that is causing the issue?

Camera is pointed at where it sounds like it's coming from, rear of the block, but I just can't pinpoint it, even with a mechanics stethoscope. Any ideas welcome, thanks.

EDIT: Can't get the video playing right in the post itself, link is below

VIDEO LINK
 
Maybe hole where the throttle shaft you're rotating goes through is worn and allowing some air to get sucked in causing the whistle when the temperature is just right.

I've never experienced anything like that on a modern car but I've seen worse on an air cooled VW carburetor because someone used too big a return spring. I don't recall there being a whistle, though.


To figure out what is really making the whistle I'd try spraying some starting fluid around everything when I hear it. It should rev up when you find it.
 
Maybe hole where the throttle shaft you're rotating goes through is worn and allowing some air to get sucked in causing the whistle when the temperature is just right.

I've never experienced anything like that on a modern car but I've seen worse on an air cooled VW carburetor because someone used too big a return spring. I don't recall there being a whistle, though.


To figure out what is really making the whistle I'd try spraying some starting fluid around everything when I hear it. It should rev up when you find it.
Interesting, haven't thought of that. I'll give it shot tomorrow, thanks for the idea.
 
Bump to an old thread, but I finally fixed it for anyone with a similar problem in the future. Local shop diagnosed a faulty leak detection pump and replaced it, but gave up trying to find the whistle, so I decided to start throwing parts at it. One new throttle body later, no more whistle, so the throttle body does appear to be the culprit, and the (apparently non-related) CEL is gone with the new pump.