FLAPPY VALVE


The "FLAPPY VALVE" is located in the intake manifold under that little black cap you see on top. The valve is used to change the intake configuration under high engine load as you hit appx 4000rpm. Like I side, Im not an expert on this car but apparentlty a bad flappy will have a big impact on engine performance!!!! CHECK IT!!!

To check the flappy operation is very simple. This is what I did.....

  1. Pop off the black cap exposing the flappy shaft, the C clip doesnt have to be removed!!!
  2. Place some tape on the top of the shaft. Shape the tape into a T so you can tell wether the shaft rotates
  3. Start the car and watch the the tape. If I'm correct you will see the tape rotate and then go back to its original postion.
  4. The big test is to accellerate the engine above appx 4000rpm. The key to this is do it rapidly, a slow acceleration wont work....the engine has to be under some load. As the engine hits appx 4000rpm you will see the tape rotate 90' as the flap opens. Once the RPM drops below 4000 it will close.
  5. Thats it....if it works, GREAT...if not you may have some work ahead of you...like i did!

The actuator for the FLAPPY is.....yes....once again....vacuum operated. The actuator is exposed to some very high engine temps and its common that it doesnt work.

Reasons Ive concluded as to why it may not work

  1. The actuator doesnt hold vacuum

  2. The line to the acuator has fallen off (as in my case)

  3. The solinoid that routes the air to the vacuum is bad

  4. The signal to the solinoid isnt present to open it

  5. or...the vavle often sticks....remove the cap, spray with some WD40 and then turn the shaft manually to free it up.

 

Location of the FLAPPY SHAFT and the cap

The Flappy actuator location.....as you can see the INTAKE MANIFOLD has to come off to get at it!!!! : ) oh.....JOY but when you do this you will have a chance to fix , clean many other components and perform quite a bit of preventive maintenance.

Close up of the actuator under the intake....

here is the "FLAPPY" closed in its normal postion. The valve fails to the CLOSED position. The other holes are the intakes inside the manifold. Its is quite an amazing design!!!!

....and the FLAPPY open....joining both sides of the intake manifold and changing the intake configeration.

This is the solinoid that recieves the signal to open the flappy. (standing front looking aft) It is located just above the right timing belt cover. I tested this by connecting 12V directly to each conection on the solinoid......you should hear a solid click!!! Next I checked to make sure it was getting a signal. I rigged up a 12V bulb and connected it to both connections and then revved the engine quickly above 4000rpm. As the signal was sent, the light bulb illuminated thus telling me the signal to open the valve was there. My problem was that the Vac line had fallen off the actuator itself, however it doesnt hurt to check other components of the system!

One good tip...when you reattach the vacuum lines to the actuator, secure them with mini-zip ties to help prevent them from sliding off...you dont want be in the postion of removing the intake manifold again.

Amazingly, even with this problem and other vacuum leaks, my car appeared to run fine and pulled strong in my eyes. However, this is my first 928 so I really dont have anything to compare it to. I cant wait to see what effects these repairs have made!

Once again...I hope this was some help to those with bad flappys!


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