Hissing whistling noise

[Gary Lewis]

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.

I don't know that it is just the time zone. I seem to have lots of conversations with myself as well.

And I think you are doing the right thing by deburring the throttle body and getting the screw lined up again.

But I don't know about the different IAC's. It will be interesting to see what difference they make if you swap them out w/o changing the TPS.

[ReneH]

I don't know that it is just the time zone. I seem to have lots of conversations with myself as well.

And I think you are doing the right thing by deburring the throttle body and getting the screw lined up again.

But I don't know about the different IAC's. It will be interesting to see what difference they make if you swap them out w/o changing the TPS.

Yes, very interesting test, cause I haven't read anything that these both are different such way. Kingfish from FSB told me last year to take the 90th version, cause these were the more reliable ones. He also mentioned that some have an internal diode...but he hasn't mentioned that they have a greater diameter.

FYI: the diameter of the 90rh version is identical to the hole in the counterpart at the plenum. The original 1986 IAC has a smaller diameter. So in the original setup from 1986 a part of the bypass bore from the plenum to the IAC was covered from the gasket. But you have to mention that I only can speak for the original 1986 302 setup.

Tomorrow we will see what's happening. I also will put no silicone to the gasket from the throttle body to the plenum. I will mount all gaskets dry, so that I can remove the throttle body and the IAC without destroying the gaskets.

[ReneH]

Yes, very interesting test, cause I haven't read anything that these both are different such way. Kingfish from FSB told me last year to take the 90th version, cause these were the more reliable ones. He also mentioned that some have an internal diode...but he hasn't mentioned that they have a greater diameter.

FYI: the diameter of the 90rh version is identical to the hole in the counterpart at the plenum. The original 1986 IAC has a smaller diameter. So in the original setup from 1986 a part of the bypass bore from the plenum to the IAC was covered from the gasket. But you have to mention that I only can speak for the original 1986 302 setup.

Tomorrow we will see what's happening. I also will put no silicone to the gasket from the throttle body to the plenum. I will mount all gaskets dry, so that I can remove the throttle body and the IAC without destroying the gaskets.

It works! Yes, it works!

My bronco idles and the engine runs. I have set the initial timing to about 12 degrees BTDC and I have recalibrated the TPS after setting the idle screw.

But I haven't got the hissing fixed...seems to be a problem of the throttle body or of the plenum...I have got cleaned all sharp edges inside the throttle body without success...

Maybe I should buy another throttle body?

But what if the hissing comes from the plenum?

I was driving today and it's fires in to exhaust when I press the pedal...do you think it's better to set more or less initial timing?

[85lebaront2]

It works! Yes, it works!

My bronco idles and the engine runs. I have set the initial timing to about 12 degrees BTDC and I have recalibrated the TPS after setting the idle screw.

But I haven't got the hissing fixed...seems to be a problem of the throttle body or of the plenum...I have got cleaned all sharp edges inside the throttle body without success...

Maybe I should buy another throttle body?

But what if the hissing comes from the plenum?

I was driving today and it's fires in to exhaust when I press the pedal...do you think it's better to set more or less initial timing?

If you do not have the hoses and air filter on, you will get a hiss at idle. The factory air intake system pretty well muffles it.

[mat in tn]

It works! Yes, it works!

My bronco idles and the engine runs. I have set the initial timing to about 12 degrees BTDC and I have recalibrated the TPS after setting the idle screw.

But I haven't got the hissing fixed...seems to be a problem of the throttle body or of the plenum...I have got cleaned all sharp edges inside the throttle body without success...

Maybe I should buy another throttle body?

But what if the hissing comes from the plenum?

I was driving today and it's fires in to exhaust when I press the pedal...do you think it's better to set more or less initial timing?

what do you mean by "fires in the exhaust"/ is your engine backfiring when you try to accelerate?

[ReneH]

If you do not have the hoses and air filter on, you will get a hiss at idle. The factory air intake system pretty well muffles it.

Hi Bill,

Ok...have you seen the video I've posted?

So I have my intake pipes and filters on...

Do you mean the intake will hissing anyway, also if I buy another one?

[ReneH]

what do you mean by "fires in the exhaust"/ is your engine backfiring when you try to accelerate?

Hi,

yes, that's exactly what I mean...sorry for my wrong translation...

But the backfire comes only when driving. While the car is in neutral or parking position, it doesn't backfire, also when warm and getting rpm up to 3000.

[mat in tn]

Hi,

yes, that's exactly what I mean...sorry for my wrong translation...

But the backfire comes only when driving. While the car is in neutral or parking position, it doesn't backfire, also when warm and getting rpm up to 3000.

wow. it really seems like the issues and symptoms keep moving around. am I correct in assuming that you deleted all air pump and emissions control? is there a catalytic converter in place? is the o2 sensor in the factory position or was it moved further away from the engine (heat source)? what type of exhaust system?

I ask these as a primer for all thinking on this with you also, as it may trigger others as to what may cause this. im wondering if somehow you are way too rich in the loaded, high demand environment adding fuel to be ignited in the exhaust as opposed to being rather lean leaving the engine. how clean are the plugs after you test drive? does the engine feel smooth or does it have any type of pulse or stutter?

[ReneH]

wow. it really seems like the issues and symptoms keep moving around. am I correct in assuming that you deleted all air pump and emissions control? is there a catalytic converter in place? is the o2 sensor in the factory position or was it moved further away from the engine (heat source)? what type of exhaust system?

I ask these as a primer for all thinking on this with you also, as it may trigger others as to what may cause this. im wondering if somehow you are way too rich in the loaded, high demand environment adding fuel to be ignited in the exhaust as opposed to being rather lean leaving the engine. how clean are the plugs after you test drive? does the engine feel smooth or does it have any type of pulse or stutter?

Hi,

you are right. No EGR and also all solenoids deleted and replaced by resistors.

No catalytic converter.

The O2 sensor is heated and mounted in the downpipe of the passenger-side.

Exhaust is stainless steel shorty-mainfolds with custom downpipes 2x 2.5" combined with a Y-pipe into a 3" muffler and tailpipe.

I will check the plugs and send photos of the plugs, my exhaust and my exhaust mainfolds.

The engine runs smoothly at low rpm while driving. Stepping on the pedal causes a power leak in acceleration and very much backfire.

So that's why I'm thinking that's a problem of the ignition timing...maybe 12 degrees too much or too less...

[mat in tn]

Hi,

you are right. No EGR and also all solenoids deleted and replaced by resistors.

No catalytic converter.

The O2 sensor is heated and mounted in the downpipe of the passenger-side.

Exhaust is stainless steel shorty-mainfolds with custom downpipes 2x 2.5" combined with a Y-pipe into a 3" muffler and tailpipe.

I will check the plugs and send photos of the plugs, my exhaust and my exhaust mainfolds.

The engine runs smoothly at low rpm while driving. Stepping on the pedal causes a power leak in acceleration and very much backfire.

So that's why I'm thinking that's a problem of the ignition timing...maybe 12 degrees too much or too less...

yes, the o2 sensor is a heated unit however it is not in the same environment that it used to be in nor is it in one like the 351 would have had. it is a much more open exhaust able to flow a lot more air and therefore much less back pressure. i like it and i have done the same on the truck I'm building but mine has a carb and no sensors. the exhaust gas oxygen sensor is very environment sensitive. it is possible that all of the components used to carry exhaust and heat away are doing too much. it seems to be getting way too much fuel for some reason. do you remember what size injectors are installed? are they the factory 19lb/hr injectors or did you replace them?