Hunting for idle/whistling at idle

[BlackBettyobs1]

Having issues with my 350 Vortec, rebuilt the motor roughly 10,000 miles ago running into an issue at stop lights my truck will surge idle in gear and will want to lurch forwards but never dies,shift into neutral idles fine.My thought was maybe it’s the distributor after the rebuild I had installed a Napa echlin distributor 5000 miles in I noticed at idle I could here a whistling/whining noise so I replaced it on warranty the whistle went away now it’s back again some days the truck runs great can barley notice it running. So I have determined that the days it runs good I can’t here a whistling or whining at a stop and the truck won’t try and lurch or hunt for idle.ANY THOUGHTS?ABOUT TO CALL IT QUITS WITH THE OLD GIRL!

 

[RichLo]

Whistling is almost always a vacuum leak. Does the whistle go away when you push the brake pedal?

Wiggle all of the vacuum lines to check for a change in tone. If no change, then spray down the intake gaskets with either brake cleaner or propane torch (NOT lit, just propane) to check for a change in RPM.

 

[BlackBettyobs1]

It’s the distributor that is making the whistling noise the noise had went away when I had replaced it on warranty but here I am again! all gaskets are fresh, bolts are all torqued proper all vacuum lines I have tested whistling stays the same with the break pedal pressed no cracks or fractures on the upper intake just strait up lost!

 

[RichLo]

I have not dealt with it before but a lot on here have had multiple problems with aftermarket distributors. Maybe its the bearings? or a bent shaft?

How does the cap and rotor look inside? is there anything rubbing?

 

[Schurkey]

spray down the intake gaskets with either brake cleaner or propane torch (NOT lit, just propane) to check for a change in RPM.

NO! DO NOT use brake cleaner:
A. Some of it is not flammable. If it won't burn, it's poor at detecting a vacuum leak into the intake manifold/air-fuel mix.
B. Some of it produces POISONOUS fumes that can injure or kill. Phosgene gas--used in WWI as a chemical weapon.

www.envirofluid.com/articles/tetrachloroethylene-a-deadly-danger-in-brake-cleaner/

Tetrachloroethylene, a deadly danger in brake cleaner

Tetrachloroethylene may be a chemical you’ve never heard of, but chances are pretty good that it’s a substance you’ve been in contact with. This is especially true if you use brake cleaner.

www.envirofluid.com

I use aerosol carb cleaner. It's easier to direct than Propane, although if the fumes get into the throttle body you'd still get a false indication.

Propane is probably safer.

 

[scott2093]

NO! DO NOT use brake cleaner

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[95burban]

@Schurkey is right, that’s why I use Crc brake clean in the green can is non chlorinated and is flammable.

 

[Hipster]

Vacuum leak was my first thought , booster diaphragm's and check valves can go bad, tbi throttle shafts etc., more difficult to find when it's sometimes. need to determine if it's a whistle or high pitched like a dry bushing/bearing noise. Like a bad idler.

 

[BlackBettyobs1]

I’m guessing it might be the bushing going out again that’s what happened with the first one I replaced on warranty any ideas on what distributor to replace Napa’s garbage with

 

[Schurkey]

The sick truth of aftermarket HEI distributors is that many of them are not drilled from the grease reservoir to the upper bushing.

They may or may not have grease in the reservoir...but even if they do, there's no passage for the lube to reach the bushing.

This is why I'd rather have a used-but-usable Genuine GM distributor than a brand-new Chinese knock-off for anything except a plastic-distributor Vortec.

'Course, that doesn't help you since you have a Vortec.

I have heard (on this forum) that there's a Made-in-USA aluminum Vortec distributor, but I've forgotten the details.

Having said all that...I've never heard a distributor whistle. I've heard them whine but it's so quiet a person would never notice over the inlet noise, exhaust noise, and valvetrain noise. So I'm still suspicious about this being a distributor issue.