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Discussion Starter #1
I have had a problem of the intake manifold moaning for about a month now on cold startups. It sounds like the noise you can make blowing through a Shop Vac hose, low and deep moaning. It lasts longer the colder the temperature is outside and stops almost instantly after about five to ten minutes. I pulled the filter cover and the sound got ten times loader so I know it is coming from the intake. I have never heard a sound like this and know it is not a mechanical sound but an air flow resonance sound. I did try to use Sea Foam spray to clean the manifold before the noise because I was getting a popping noise one time before the moaning sound. The popping sound was after a 20 mile trip. It stopped and now moaning.

I am starting to think it is related to the runner control in the 2006 manifolds but don't know enough about the way it works. I did remove a vacuum hose by the runner controller and sprayed Sea Foam in to try to clean that side of the manifold. I will see if this works on the next cold start. THERE ARE NO ENGINE CODES.

Does any one have info on the intake and how the runner system works and when it switches.
 

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Discussion Starter #3 (Edited)
^ Thanks for the info but not sure a Vulcan engine operates in that manner. I have done a little research on my own and believe on a Vulcan it is limited to an actuator and a butterfly valve on the back side of the manifold. I know you have a 2006 and it is on the passenger side of the upper manifold near the PCV valve. It is held in by two #30 torx screws. It is a cylinder that has a butterfly valve that must change the length of the runners based on the speed. I don't think it operates like a duratec engine with two runners per cylinder. I have found out that the o-ring that seals the actuator is prone to leaking and causes quite a few problems with misfires. I will be buying a new o-ring from Ford Part #87072 S91 and replacing and cleaning the valve. I didn't know this car even had this. I attached a few pictures of where the valve is located.
 

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Discussion Starter #4
I was tracking down the moaning sound on my intake and I started to get a popping sound again in the intake. It seems to go away when I pull the power brake booster hose off of the intake manifold. I pull the hose and put my finger over to intake manifold hose connection. This hose goes to the vacuum distribution box and feeds the power brake booster and more. Any idea what could cause the popping sound. It is a rapid sound that is inside the intake air tube. Sounds like a check valve of a solenoid cycling and the valve is causing a noise through the booster hose.
 

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I did not find just what I was looking for but brake booster moan or popping produces some info on google. I will post a link if I find something spot on.
 

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I'd put a vacuum gauge on it and see what it says. Maybe you have a valve that is sticking a bit or something?

The thing on the gen 4.5 vulcan manifold is a tuning valve (IMTV). It turns 90º via the motor to change the intake tuning. Maybe you want to take that out and make sure it's not all carboned up.
 

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Discussion Starter #7 (Edited)
Thanks Tom and Behlinia. I pulled the intake a month ago and did a off car cleaning and looked at the runner control valve. All looked good. That valve opens at a higher rpm than what I start to hear the noise at. If I pull the IAC connector the the popping nearly stops. I don't think it's a intake valve sticking because it happens multiple times a second which would mean all valves sticking. I started to think a sticking booster check valve even though the brakes are fine. It also has a rock steady idle, can't see the tach needle move at idle.

I will start isolating the lines from the vacuum distribution box to narrow down the source

What sets the idle at 500 rpm when you disconnect the IAC connector. Is it just a fixed position on that valve. It seemed earlier year valves would shut off completely
 

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Thanks Tom and Behlinia. I pulled the intake a month ago and did a off car cleaning and looked at the runner control valve. All looked good. That valve opens at a higher rpm than what I start to hear the noise at. If I pull the IAC connector the the popping nearly stops. I don't think it's a intake valve sticking because it happens multiple times a second which would mean all valves sticking. I started to think a sticking booster check valve even though the brakes are fine. It also has a rock steady idle, can't see the tach needle move at idle.

I will start isolating the lines from the vacuum distribution box to narrow down the source

What sets the idle at 500 rpm when you disconnect the IAC connector. Is it just a fixed position on that valve. It seemed earlier year valves would shut off completely
When you unplug the IAC, it should get sucked closed so that the only air keeping the engine going is the air coming through the small gap in the throttle plate. Unplugging it should be the same as removing the IAC and covering the holes. If it doesn't stay running in that state, you have a vacuum leak, the throttle plate is dirty, or it isn't adjusted properly.
 

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Discussion Starter #9
When you unplug the IAC, it should get sucked closed so that the only air keeping the engine going is the air coming through the small gap in the throttle plate. Unplugging it should be the same as removing the IAC and covering the holes. If it doesn't stay running in that state, you have a vacuum leak, the throttle plate is dirty, or it isn't adjusted properly.
It seems that on the 2006 the throttle plate is a tight shut off and the IAC actually does not provide a tight shut off. There is a small hole, maybe a 1/16 of an inch but that is not enough to feed an idle of 500 RPMs. Maybe there is a groove cut in the top area of the throttle body to bypass air.
 

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What I remember from when I had mine off was that the throttle plate shut off the air it seemed, not for sure though.
 

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Discussion Starter #13 (Edited)
Well it seems that the IAC is the same in my 2006 and my 2001s so it looks like a swap to see if it has anything to do with the noise is in order. Motorcraft CX1946 is listed for both in Rock Auto.

I looked at the pictures of the throttle bodies and they look like a tight shut off.
 

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Thanks Tom and Behlinia. I pulled the intake a month ago and did a off car cleaning and looked at the runner control valve. All looked good. That valve opens at a higher rpm than what I start to hear the noise at. If I pull the IAC connector the the popping nearly stops. I don't think it's a intake valve sticking because it happens multiple times a second which would mean all valves sticking. I started to think a sticking booster check valve even though the brakes are fine. It also has a rock steady idle, can't see the tach needle move at idle.
A bad brake booster check valve won't cause braking problems, unless there is no flow thru it, or the engine happens to back fire while braking. (Not a likely scenario). That's what the check valve is for.
 

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Discussion Starter #15
Well I isolated the brake booster and climate controls vacuum lines and the popping noise is still there. I swapped the IAC with one on my 2001 and still the noise is there. I recorded the popping sound by placing the camera in the filter box. The sound recorded like wind noise on a mike but that's the sound you hear with your ear. Hopefully this works, it's my first video upload.

MVI 9677 - YouTube
 

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Totally not what I was expecting there is no consistency to it at all. Only crazy idea I have is PVC system.
 

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Discussion Starter #17
I was listening to the PCV system and didn't notice the sound at the PCV valve. I don't think it is a leaking intake valve either. It is a little sharper of a sound in person but it random frequency and doesn't seem to vary much with the increase of RPMs. I don't hear anything in the EGR valve either. Maybe the EVAP system.
 

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Totally not what I was expecting there is no consistency to it at all. Only crazy idea I have is PVC system.
It does sort of remind me of a coffee pot once it runs out of water and the remaining water boils in the tube. Disconnecting the PCV is worth a shot, IMO.

Can you feel the vibrations from it if you put your hand on the intake?

Otherwise I have no clue.
 

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Discussion Starter #20
I used a stethoscope to listen to every part of the engine and there is no noise from any where. I will check to see if the intake has a pressure pulse with the noise however it is so rapid I don't expect one. The intake valves are all not burnt. I am really thinking it is fuel injectors at this point.
 
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