Z928328

here's the vid
the sound is trace at the throttle body area

atari_st

I just did a refresh on my 87 and it is dong the exact thing. Runs great but I know something is not right. I have sprayed starter fluid around each port and nothing appears to be getting into the intake. Can't get to the throttle body unless I take the time to remove the air box...which may be next.

MainePorsche

That sounds like a large efflux of air, more than I would think would come from a split vacuum line off the plenum. My bet would be one of the gaskets (either plenum to manifold, or manifold to block).
Yes, the manifold will have to come off again.

MainePorsche

Also make sure your MAS cylinder is well seated in its rubber ring, and your airbox MAS entry point is well seated into the top of the MAS. This is easy, and you can do without going to the mechanic. Only requires removal of the airbox.

Z928328

But ever since I change the manifold gasket- The car idles much better & smoother & felt like more power from the engine. It's only the sound that annoys me.

So I may need to change the manifold gasket again you mean? you mention "Manifold to block"? or its a different gasket?

One thing when they change the manifold gasket. For 2 days- I do not have this sound.

The airbox- we check already. all was good. and tight,

MainePorsche

Manifold to throttle plenum - gasket 6
Manifold to block - gasket 8

Adk46

I've had a similar noise. No idle or running issue I could detect, just the noise.

I'm in the middle of an intake refresh. I thought I would find something obviously amiss, but I didn't. I'm hoping that careful re-assembly with new seals etc will make the noise go away. Assuming it ever runs again, that is.

Z928328

I guess I should get gasket 6 then? I already change gasket 8.

zekgb

Not sure if this will cause a whistle, but the throttle body bearing seals are a common source of vacuum leak and could be magnified when he rest of the system is properly sealed. See this writeup for detail along with a test rig.

Mike Frye's Throttle Body Seal Thread

Porken found his ICV valve whistled and it went away once he adjusted the idle speed at the throttle body.

On my car post refresh I had a whistle that was caused by my not removing primer from the mating surface of my freshly powder coated intake runners so an improperly sealed intake is also definitely in play.

the flyin' scotsman

if you had the throttle body off previously then the gaskets(#6) should have been changed.

are the ISV hoses new? if so were they carefully heated before install (hot water works well). The hoses are prone to splitting.

As mentioned there are the 2 Oring bearings on the throttle body shaft......these should also be replaced with the newer double Oring bearing.

Good luck

mark kibort

that aint no vacuum line for sure... its like something is in the air stream around the maf. Mine has been howeling about twice as loud as this for a couple of years now and i have never been able to pin point it. the throttle body gasket sounds likely, but i havent put the carb cleaner test to use here.

dr bob

Easiest way to find intake leaks is to build one of the test fixtures in Dwayne's Intake Refresh tutorial. Add a little compressed air, stir for effect...


Just a reminder that these really are vacuum (air) leaks, places where unmetered air is drawn into the intake while the engine is running. In closed-loop operation (after the engine warms up, but at idle to part-throttle only, your working oxygen sensor will do some compensation. Off of closed loop operation, no compensation, and things go lean.

Adk46

I couldn't get the 2-to-4-inch rubber pipe reducer to fit over my MAF. I am aware that pipes have OD's different from nominal, but I thought all "4-inch" pipe had the same OD regardless of schedule. Is there a plumber in the house?

Z928328

thanks for the suggestions. I'll be printing this.

But today I was driving the car around town to get a pizza. Suddenly when I was reversing into my garage- The car was shaking- The RPM went down but it didn't stall. I rev it up- The engine felt like no power. I did a drive again- The engine felt no power at all when accelerating(limp mode?) & when I stop at the junction- The car shakes. I drive back home- & let it idle for few minutes- It shakes but didn't stall.

So this no power engine, car shakes, related to the whistling?

Makes me wonder what if I didn't change the manifold gasket- I will not encounter this headache?

dr bob

Z928328 PM'd about the shaking issue. I responded to look at the Ignition Protection Relay and the reasons it might activate. This is separate from the air leak issues with the gaskets.