Odd whistling noise at idle...

[Down by the Water]

Anyone have an idea what might be causing this?

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I just finished new head cover gaskets, re-bedded halfmoon seals, new cam plugs, spark plugs and wires. Also, new air plenum gaskets and I replaced a couple cracked vacuum hoses. She runs perfect but is now making this odd whistling sound?

I tried shutting it off and turning it back on...again, runs great, idles smooth...I'm even having trouble locating it? Seems strongest on passenger side, but not definitive.

Thoughts?

 

[Devbot]

I'd put $10 on your airbox lid not being fully seated, or perhaps not fully seated into the intake hose.

 

[mtbtim]

That could be a pulley bearing on it's way out. Get yourself a mechanic's stethoscope and it will help you narrow down the source of the noise.

This is the one that I own: Amazon.com: Lisle 52750 Stethoscope Kit : Everything Else

 

[brillo_76]

Yup you have an intake leak. Verify all your hoses are on that your main intake hose doesn't have a crack in it from old age. and all your vacuum lines are good and on. If you cant find it. Then use wd 40 and gently spray around your intake etc. If you hit the leak the the whistle will go away for a second and your speed up a second or two. That may help you find the leak.

 

[jgue467]

Usually intake leaks lead to a P0171, does your have one set or pending?

Mine needed the 'hose' closest to the intake plenum, see pic below. It can develop a crack in one of those large bends, can't really see it until its spread apart some yet it is there enough to cause a leak and mess up the A/F mix. Luck.

 

[spartacus]

Wouldn't hurt to check the pcv valve, grommet and hose.

 

[Garandman]

The usual diagnostic tool is a few feet of tubing. Hold one end to your ear and move the other end around to see if you can localize the leak. Then spray some soapy water in the area if it isn’t obvious.

 

[19963.4lsr5]

Wouldn't hurt to check the pcv valve, grommet and hose.

That was the problem on the 97 puppy hauler. The rubber hose got soft and sucked flat causing the noise.


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[Down by the Water]

Brillo_76 you are the winner!!

Had some time this morning to spend with the old gal.

She did throw a P0171 code earlier this week. No other related codes. So, I cleared it. Freeze frame data says fuel trim is off, which makes sense if it's running lean because of unmetered air. Nothing else notable. This morning, I double checked everything, vacuum hoses, air intake, etc...and could find no smoking gun. Once it warmed up the noise came back. I sprayed a little brake clean around, and right at the base of the plenum the noise went away and the engine shuddered a bit. I sprayed several more times, same each time.

I was able to get a socket on the bolts to both sides of where I estimated the leak to be. I tightened them down a bit and the sound is gone. It is still sucking air (squirting brake clean still makes it run a little rough) but I know where the problem is. I'll take the plenum apart maybe tomorrow, chase all the threads and make sure everything is installed and torqued to spec.

Thanks to everyone who offered their help. Brillo, if ever you're in NE Florida, message me. I owe you a beer ;o)

 

[brillo_76]

Had some time this morning to spend with the old gal.



She did throw a P0171 code earlier this week. No other related codes. So, I cleared it. Freeze frame data says fuel trim is off, which makes sense if it's running lean because of unmetered air. Nothing else notable. This morning, I double checked everything, vacuum hoses, air intake, etc...and could find no smoking gun. Once it warmed up the noise came back. I sprayed a little brake clean around, and right at the base of the plenum the noise went away and the engine shuddered a bit. I sprayed several more times, same each time.



I was able to get a socket on the bolts to both sides of where I estimated the leak to be. I tightened them down a bit and the sound is gone. It is still sucking air (squirting brake clean still makes it run a little rough) but I know where the problem is. I'll take the plenum apart maybe tomorrow, chase all the threads and make sure everything is installed and torqued to spec.



Thanks to everyone who offered their help. Brillo, if ever you're in NE Florida, message me. I owe you a beer ;o)

Glad you found it. Brake cleaner etc has help me alot over the years... I am mostly stuck here in PA. But if I am down that way. I let you know...

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[Endlessblockades]

Timely post! I have been having an A/F mix issue and low idle from time to time. I just started hearing this weird Jetson's saucer/whistling noise for a good part of a 150 mile drive. I found the filter flap on my airbox open the other day, too....gonna take a look at the whole air intake tube. Funny thing - 2 days after I bought this 4Runner I found a crack in the intake air elbow as pictured above and replaced it.