I need some advice on my intake restauration project. I had to completely disassemble the entire intake (due to my shop putting sand in there... but that's another story).
Now that it's all cleaned up and painted I have some questions.
I took out the, what I assume is called the flappy valve and it seems to be controlled by a small vacuum membrane. I cleaned and greased the bearings and reassembled it. If I let the flappy close itself shut fast, it kinda sticks a bit when trying to open it again.
Is that normal and it simpply does not close that hard when in normal operation or do I have a problem?
And my idle control unit looks pretty bad and also had some sand in it. That seems to be a rather costly item. How can I test it?
Any help would be greatly apreciated.
regards,
Sab.
'87 S4 auto 116k miles waiting on replacement engine to be installed.

 

Sab,
You can find the tests and temporary(?)cure
for the 'flappy' valve in the archives. Let me also recommend The Greg Nichols site. I'm not sure what you mean by the IDLE CONTROL UNIT. unless it's either the Air Mass Sensor or the Fuel Pressure regulator. If either of those has been pounding sand where the sun never shines, has sand in it, and you have every thing apart.
Consider:
Rebuilt Air Mass Sensor minus the hot wire costs-
$395.00, and the Fuel Pressure Regulator around-
$70.00. This is thru 928 International.
Also,I am, fairly, positive that you will have to apply vacuum at the specified levels to the actuator with the'flappy hooked-up to see that it is operating correctly.
hth/lol
John S. and Pattycakes

 

It's a shame that Phil Tong doesn't participate here - he's the reigning 'Flappy King'.

 

John,
I was refering to the the idle stabilizer.
928.606.161.01 (Sits right on the throttle valve housing under the intake)
After cleaning it it looks fully operational, but I would like to test it, since it would be quite some work to find out after getting it all back together that it doesn't work.
regards,
Sab.

 

Sab-

In as far as the Idle Stabilizer testing is concerned - I do not know of a good way to do this with it out of the control 'loop'. Even with the cleanup of the sand, i would replace it anyway. A new one is ~$195 - and as you have found out the only way to replace it is pull the Intake. Something else to consider while ytou're under there are the Knock Sensors and all of the vacuum lines.

The Resonance Flap (i.e. 'flappy') valve is spring return to close. This valve is controlled by vacuum via a solenoid located on the Driver's side front of the engine (solenoid is mounted to the Cam belt cover). The valve will initially open and close when you turn the key to the on position (excellent troubleshooting tip here) and is desinged to open between ~3500 and 4000 rpm under full load conditions for a second ummmpphh in the power department. Just like the knock sensors and the age factor - I would recommend replacing the vacuum pod for the flappy WYAIT (unless it hase been replaced in the last 30K or so). As for the 'stickyness' of the flappy when you release it from fully open and allow it to close - I don't think that it should 'stick'. HAve you cleaned the seating surfaces of the flappy real well? Just a thought...

hth-

 

I agree with all of the above responses. With 116k on the clock you will be far better off to replace with new as much of the under the intake stuff as you can afford.

I don't know what your skill level is, but you may want to disasemble the "Flappy" and lightly clean the shaft and bearing surfaces with Scotch brite. The "flappy" should be smooth as butter in both directions. Also check the vacuum pot linkage and see if it is bidding.

Sand is nasty stuff, it seems to gets into everything. When you try to clean it out it just doesn't want to budge. But you know that any that you leave "WILL" come loss and find it way into the motor to do more harm.

HTH

Max

 

Can a flappy that does not move freely create a humming/whistleing noise on idle - maybe when air passes through a not all-the-way closed flappy?

 

Nicole, you can test easily according to Tony. Check his site.

<a href="http://members.rennlist.com/v1uhoh/Flappy.htm" target="_blank">Tonys</a>

 

Nicole,
Agree with the above.
You might want to check the intake tubes,
and the crank breather hose (?) going into the right lower side of the air filter box. And it's possible, we all make mistakes, that the filter was misaligned at last installation/service.
In any of these cases the vacuum from those 8 pistons would be sucking air thru a RESTRICTED amount of space. Depending on RPM the sound would vary. Try sucking air thru closed teeth slowly at first then faster. Notice the pitch and sound change...? Count your blessings ... back in the mid 60's the Oldsmobile Jetstar V-8's sounded like an aircraft start cart/APU exhaust and crackeled and snapped, too!
Nicole, one last thing -do this first- start the sHARk, don't wait for it to warm up, pop the hood center yourself at the front of the car then place your hand on the top of the intake manifold turn your head so your listening with one ear.
Lift your hand and move it to another spot on the intake while keeping your head locked in place.
Now move to either side and repeat. I've tried this on a number of sHARKs and the result is the same. Either the hand is dampening the sound of air rushing thru the intake or it's blocking the sound of an intake gasket leak , but the sound does disappear while you are doing this.
later, hth
John S. and Pattycakes

 

Sab,
The idle positioner makes idle speed adjustments; electronically, it is bolted under the throttle housing. The only effective way of diagnosing is with an oscilloscope since it receives ground pluses via LH CONTROLER of 100HZ.

Nicole,
It sound like a vacuum leak, one way to check is with carburator cleaner,
With the engine running spray carburator cleaner in the area you hear the leak, if there is an increase in engine speed you have a vacuum leak.


Steve C
The Great White

 

Steve,
Thanks, I hadn't thought of that to smoke out the evil intake leak.
But, for sure, on Pattycakes it would have to be the lower gasket. I checked EVERYTHING else.
It's never easy...
John S. and Pattycakes

 

Upon startup, the flappy turns about 80 degrees on my car. Is that as much as it is supposed to move, or should it move a full 90 degrees?

When I pull the vacuum line in front of the engine, the flappy does not move at all. So I know there usually IS vacuum.

The whining sound might come from somewhere further down in front of the engine, drivers side. Maybe it is the alternator? The whining seems to disappear completely when the engine is reved. It might not be a big deal - I just noticed that another S4 did not have that whine.

 

Nicole-

The flappy will open a full 90, but not necessarily when the engine ignition is switched on. The test is a pulse - and is so short in duration that the valve never completely over comes spring pressure to position fully before the vacuum is removed (note - vacuum is crucial for proper operation of the flappy).

Just to see if it does fully reposition, pop off the vacuum line to the actuator and using a MitiVac pump, see if you can reposition the valve to the fully open position.

hth-

 

Thanks, Jay! Since a "MitiVac pump" is in every girl's purse, I will try this right away... Just kidding!

No, I don't have one of these. Right now the car isn't running anyway, because the injectors are out to be cleaned and balanced. Maybe that'll bring a smooth idle back, and avoid further gasoline smell of the oil?

 

Just a thought on the method proscribed for finding vacuum leaks using spray carb cleaner--

If the idle air control solenoid is working correctly, the idle speed will stay constant even when the leaking air is 'richened' with carb cleaner or starting fluid or gasoline. However, this is the method of choice for engines with a fixed idle speed, like those cars with carburetors.

A possible solution is to prop the throttle open slightly, raising idle a couple hundred revs so that the IAC stays completely closed. Then, adding fuel to the air going in through the leak may cause a noticeable speed increase.


As always, there's the dr's safety reminder about keeping the charged garden hose very handy, and working outside the garage whenever you spray flammable stuff around a running engine. The mess from the garden hose is a --lot-- easier to clean up than the fire extinguisher chemical. Don't ask me how I know this...