Hissing whistling noise

Hi, now that seems all to be fine, the hissing noise coming from the throttle body is back...I have had found a vacuum leak before directly in my MAP line and solved it.

Now my question is if someone have had heard such a sound before. My suspects are another vacuum leak or something with the throttle body.
YouTube 


I have given the body for cleaning to a company that also has cleaned my engine, cause of the real big amount of deposits inside. They also have done the bore for the stroker kit.
It's off-topic, but so it looks a half year ago:

not sure that I'm understanding the question but that is one "nasty" engine!
I would suggest the old trick of using a length of hose as a stethoscope and track down exactly where the whistle is originating from. it is very possible for a stroker to pull hard enough on the throttle plates to find a "whistle point."

It sounds that it comes directly out of the throttle body. I can get rid of it when opening the throttles to the maximum the idel screw let me do. Maybe it's caused due the cleaning of the throttle body?

Also the engine runs not good in idle. Rpm going up and down. At the last starts it dies sometimes in idle...

Maybe I need to drill the throttle plates, cause of the stroker? As I've said, I have the 302 throttle body...

So that's why I suggested another vacuum leak...I have already sprayed every connection and also all parts of the mainfold which I can access. No real change of rpm...so there seems no leak.
Maybe at the cabin or at the C6.

Btw: what does the vacuum vent do at the gearbox?
Currently I also can set so gear. Maybe too less oil (about 9 liters inside since filter and oil-pan change)...

if you are concerned about a possible vacuum leak in an accessory circuit then that is real easy to test. just locate the circuit and cap the port at the intake. it will eliminate that circuit and tell you which has a leak if it is that. the brake booster is also a possibility. however, I don't see an accessory vacuum leak causing the throttle body to whistle. and if it runs/starts better with more air then the afr is off. now that it is running it is behaving as if you have an incompatible camshaft for the ecu. im sure that this was tripple checked and discussed much earlier in the troubleshooting process

Hi!

ok, I will deactivate all vacuum circuits one by another and check this.
But what if the mainfold gasket is the problem? As I've said, I have sprayed everything I could reach.
To reach the backside of the mainfold between the firewall isn't very easy.

But I'm wondering about the camshaft...I have a 351W stock camshaft and also a 351W stock ECU...should't they work together better than a 351W cam with a 302 ECU?

What do you mean with afr?

Hi, Regarding the throttle setting/idle screw I have found this: I will try this after testing all vacuum circuits for leaks. But I have to admit, that I have not understood to 100 percent, what's to do...especially these plugs...I think I don't have them...

I have checked the vacuum lines...no change if I clamp them.

But I have read a lot...as you see in my post before. I also find much people that use this part to adjust the idle
eBay

It seems to be a common problem with the throttle body...also sharp edges can cause the whistling...so I think I have some at the bore of the body to the IAC...

My unsteady idle can also be a problem of ignition timing...maybe 12 degrees are better as using a Stroker.

I also have measured the voltage between IAC and VPWR. 0.5 volts while idling at about 1000rpm. I don't come down much more, cause the engine will die otherwise...so many it's really not enough air coming in.

Maybe I should try to bore the 2mm holes inside the plates, like Bill told me to do.

I will unmount the body, make the bore and also clean the sharp edges as next.

Interesting!  I've never seen that part, but I probably have TSB 91-25 and can post it tomorrow if it'll help.

imagine that. somebody makes an idle air bleed to compensate for the iac. a tunable vacuum leak! again, you do not have a 351w. you have a heavily modified 5.0. the intakes on the 5.8 are much smaller than the 5.0 and the camshaft is larger than the truck 5.0 camshaft. this has everything to do with velocity inside the individual intake runners. the 5.8/351 was built and installed in heavy vehicles expecting a slower throttle response under a load yet the ability to keep up engine vacuum while doing so. all accesories need vacuum. the 5.0 on the other hand has larger rectangular ports and a larger volume in the intake which relates to the vacuum available for throttle response. consider the mustang. they took the 351w cam and installed it in the 5.0 and tuned it accordingly for a 3200 lb car expecting it to be "wound tight." I would not be surprised if the 5.0 ecu would not run this engine better. the camshaft you listed says stock replacement but not for a 5.0. only for a 5.8. it is greatly increased over the broncos original camshaft. if you were building a carbureted system or even a sniper then you would not be in this situation.

Hi!
Thanks for the information. I understand what you mean.
I had the opinion that the throttle body of the 351W and the 302 are the same. Also the IAC and the TPS.
I know about my situation and it wasn't planed in this way...I opened the intake mainfold, cause two outlets were wet from oil...you have seen upon, what I have seen.
The whole block looks like this. Two connection rods were bent, the cylinders had piston tipper. Alle crankshaft and camshaft bearings were worn out...
So i tried to get stock parts, but without success..neither they aren't available nor very expensive...so it comes to the stroker kit. I have completely reworked the whole engine and nearly changed all parts at it.
The most parts selected with the help of people from the FSB board...as they were with the latin at the end, they told me about this forum and that there are specialists regarding the EFI engines...so, thats my story...

But back again:
After checking the accessories vacuum and found no leak, I will unmount the throttle body and rework the sharp edges...I have already read in the past about problems after cleaning the throttle body. As I've bought the car all edges were covered with deposits...all fine smoth edges, like a coating. Now everything  is nice and clean but also sharp...especially the bore of the IAC bypass.

What does the book mean with this orifice inside the blades and about to plug them or not "plug select from go/no go using gauge pegs"
Does this mean, that there are throttle plates with pluggable holes inside that can be removed or plugged to adjust the idle airflow?

I had that exact kit on my 1990 Lincoln Town Car with the last of the 302 speed density sequential injection systems. Same issue, inability to get the idle speed high enough without getting the TPS voltage too high.

The hissing sound from the throttle body is due to the air going through a narrow opening at high speed. If you take a small hose and hold it near your ear, the same sound is in a carburetor, you have to get the hose into it far enough to hear. I synchronized many a set of multiple carburetors (SU, Weber, Zenith-Stromberg, Rochester HV, Carter YH) that way.

As for the engine not wanting to run correctly below 1000 rpm. it could be a TPS voltage issue, or, if the cam has too much overlap/duration, the vacuum may be pulsing too much which will cause problems.

Hi Bill,

ok, that sounds good, as you seem to know the problem. So what was your solution for your 1990 Lincoln Town Car? Was it thisone you have done the 2mm bore into the throttle plates?
What do you think about the IAC spacer-kit? May that solve the problem?

OK, so my next step to unmount and smooth the sharp edges will not be bad at all...

About the cam: Is that possible? Like posted in another threat, it's a 351W stock cam. Has this cam so different overlap/duration across
From the original 302 cam? As far as I have read while buying the stroker kit from summit, they prefer much more aggressive cams for the kit. As I don't want to build a racing car, I've decided for the stock of the 351W, to have better times for the valves regarding to my bigger displacement.

Is there any way to remove the cam from the suspects?
Have I told you, that I use an adjustable timing chain?
Currently set to factory 0 degrees.

Rene' the 1990 Town Car I used the kit on, it mounts between the IAC and the throttle body. The one I drilled the holes in was my son's 1986 F150, essentially the same setup as your Bronco, just had two fuel tanks. His issue was the throttle opened far enough for a good idle would put the TPS voltage high enough to cause the EGR solenoids to "chatter" and as they did the idle would surge as the system tried to find it's best balance. Part of the issue was his TPS, he had bought an aftermarket one and it read high at closed throttle. Once he purchased a Motorcraft one the problems went away.

We drilled a pair of 1/16" holes in the throttle plates if I remember correctly.

Do you have the specifications on your cam? These speed density EFI systems are extremely sensitive to cam duration, overlap and lobe separation.

Hi Bill,

Ok, now I understand. So the plate is maybe an option to control the idle. But as far as I understand this distance plate, drill holes into the blades will have a nearly similar effect.
My TPS seems in range...only about the upper value I'm not 100 percent sure. About 4.38V...is this too low?

I have bought this cam:
Summit
The values are:
Intake Duration at 050 inch Lift: 210
Exhaust Duration at 050 inch Lift: 214
Duration at 050 inch Lift: 210 int./214 exh.
Advertised Intake Duration: 254
Advertised Exhaust Duration: 258
Advertised Duration: 254 int./258 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.478 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.485 in.
Valve Lift with Factory Rocker Arm Ratio: 0.478 int./0.485 exh.
Lobe Separation (degrees): 114

So also about the 10 degree BTDC I'm not sure...maybe my setup should be better with 12 degree?

Rene' here is what I dug up quickly on Speed Density Ford systems: https://www.corral.net/threads/speed-density-camshaft.788163/ 

I know when we were building my new engine, the builder prefers Sig Erson cams so we placed a call to Sig Erson and his very first question was "how much tune ability do you have in that MAF system?" The cam he sent is here:

Hi Bill,

Ok. Thanks for this. Reading this article shows in my opinion, that my cam values seems to be in range.

And I'm still thinking it's a matter of air combined with maybe a too small base timing regarding the idle.

So, assuming this and I hope you are with me to this theory, I have still the two options:
1. Drill holes into the blades.
2. Buy a adjustable IAC spacer.
With one if this modifications I play it save, that my TPS idle value will not get too high.

I'm also be able to remove my current TPS and set my old TPS to 1V, without mounting it to the throttle body, to simulate closed throttle, independent to the throttle position. So I should  be able to check, if there gets too less air inside while idling...

But regarding the TPS, there is still my question left, if my maximum TPS value is too low with 4.38V.

your peak voltage return of 4.38 will have no effect on the issues that you are experiencing. at best it will show up at wide open throttle under a heavy load.

Hi, you are right. Nothing that's regarding my current issue. But if I know by now that 4.38V isn't enough for registering the ECU a wide open throttle, it will be the next problem.
I only try to work one time at one part...if possible...so I want to avoid to work on the TPS again, if I can be relatively sure by now, that my maximum voltage isn't enough...

So, that's the aim of asking for this right now.

So, I  reply myself...I have found this in my new Bible...


So it seems my TPS upper voltage is absolutely in range. I also seem to have enough space in the closed value.

So I will proceed as planned and unmount the throttle body and clean the edges at first.

So I see...the time shift leads me to talk to myself...

I have cleaned the throttle body out of sharp edges:





I also have bent the counterplate of the idle screw back to parallel to the body;


So I will set my basic throttle opening again to about some steps below 1V, if I'll still reach about 4.5v at fully open throttle.

And I have figured out that the 90th IAC has a 3mm greater bore of the inlet and outlet compared to the 1989th version.


I will first mount the 80th version without silicone to check if there is a difference. Both are also internally different. I my opinion the 89th version seems to close better and also completely. The 90th version seems to be stuck open  a bit, also when no voltage applied.