Resonant flap sticks-what to do?

[sandiego]

I understand I have a resonant flap on my 91 engine which operates around 4500 rpm. I reached behind the manifold and tried to rotate the external arm which connects to the flap. The initial movement was "stuck" more than I think it should be-probably more than the vacuum device can overcome. After that it rotates easily.

Question: How do I get to the source of the resistance? Is the flap itself binding on the manifold? Are there bushings on the flap shaft which wear? Do I have to remove the whole center section between the left and right manifolds? Other ideas?
Thanks

[ischmitz]

I don't think actuating the flap by hand is the proper way to test it. You also work against the actuator resistance.

You need the hammer or PST2 to actuate the flap. Else, with an intact vaccum system on the car (no leaks) the flap once actuates when you turn the ignition to ON. It uses the resiudual vaccum stored in the vacuum canister. To test, run the engine, shut it down and the have an asistant turn the ignition to ON without cranking while you watch the flap. You should see it moving once.

Ingo

[sandiego]

I'll try that.
In fact I did not have the actuator arm connected-just rotated the flap clockwise and only had the binding at the initial fully CCW position. I suppose it is possible that the flap never reaches the fully CCW position when the arm is connected and therefore wont get to the point where it binds. We'll see.

[ischmitz]

Hm, you could have some oil sludge in the crossover pipe where the flap sits that makes it stick in its closed position. Every time someone overfills the oil it gets sucked into the intake. Even w/o overfilling oil mist gets into the intake through the breather tube from the oil tank.

When I have had my engine appart the intake was wet and sticky on the inside. However, it is a ****** to remove the intake with the engine in the car... but that is the only way to tell what's really going on. Let us know what you find.

Ingo

[Oracle]

If when you turn the ignition on you can hear a click that means its working fine, its part of the startup to open/close the flap to get it unstuck. Don't force it with your hand if its still attached to the actuator.