Resonance Flap Problem
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From: Cheshire, England
Resonance Flap Problem
Seems like an age since I actually posted due to a problem with my car...
Whilst on the North Wales Run, I realised that my resonance flap seemed to have stopped operating. I can't say I noticed any reduction in performance, but the 'step' and noise-change in the power delivery around 6000rpm went AWOL.
Can someone point me at just where to look to check for the Res Flap connection (is it a vacuum connection, an electrical wire, or a mechanical rod/linkage) to see if it's OK?
Whilst on the North Wales Run, I realised that my resonance flap seemed to have stopped operating. I can't say I noticed any reduction in performance, but the 'step' and noise-change in the power delivery around 6000rpm went AWOL.
Can someone point me at just where to look to check for the Res Flap connection (is it a vacuum connection, an electrical wire, or a mechanical rod/linkage) to see if it's OK?
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From: Parafield Gardens
Dear John,
Again pictures are in my book. Chapter 4 under air intake I think.
The reasonance flapper valve is part of the air intake. It uses a solenoid valve operated vacuum supply to the flapper valve itself.
Inotherwards the DME electrically activates the solenoid which opens and allows vacuum through to operate the valve. Now called change or switch over valves. They do fail by the way.
You will see the linkages and on yours it is easier to see because you have the aluminium air intake.
The most common failure is the solenoid valve but it could be as simple as the vacuum line has come adrift.
Ciao,
Adrian.
Again pictures are in my book. Chapter 4 under air intake I think.
The reasonance flapper valve is part of the air intake. It uses a solenoid valve operated vacuum supply to the flapper valve itself.
Inotherwards the DME electrically activates the solenoid which opens and allows vacuum through to operate the valve. Now called change or switch over valves. They do fail by the way.
You will see the linkages and on yours it is easier to see because you have the aluminium air intake.
The most common failure is the solenoid valve but it could be as simple as the vacuum line has come adrift.
Ciao,
Adrian.
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From: USVI
You can tap the two-pin connector on the vacuum solenoid with a 9-volt battery to test it and it should make a clicking sound if the car is not running. If the engine is running and at idle the idle speed should change but you won't hear a click. 
You should also be able to see movement of the mechanical arm linkage below the throttle body that's connected to the resonance flap (if the engines running). It is possible for the mechanical arm to bind where it attachs to the flap so use your hand to move the arm back and forth, it makes a "plop, plop" sound when it opens and closes.
You should also be able to see movement of the mechanical arm linkage below the throttle body that's connected to the resonance flap (if the engines running). It is possible for the mechanical arm to bind where it attachs to the flap so use your hand to move the arm back and forth, it makes a "plop, plop" sound when it opens and closes.
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From: Cheshire, England
Thanks, both!
Don't know why I didn't think of opening your book once more, Adrian!
Why are the bits you need to see always hidden round the back of the engine?!
Don't know why I didn't think of opening your book once more, Adrian!
Why are the bits you need to see always hidden round the back of the engine?!
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From: Parafield Gardens
Cause that is what makes a Porsche a Porsche. Besides they had to put this stuff somewhere 
Ciao,
Adrian.
PS: You see the vacuum line in Jason's picture. I have seen quite a few of these cracked. They look okay but when you pull them off and give them a bit of a stretch the light starts to shine through. Please all remember that our 964s are getting old. Hose and vacuum lines all age with the heat, time and the environment and they will all require replacing.
My 1989 is due for hose replacements.
Ciao,
Adrian.
PS: You see the vacuum line in Jason's picture. I have seen quite a few of these cracked. They look okay but when you pull them off and give them a bit of a stretch the light starts to shine through. Please all remember that our 964s are getting old. Hose and vacuum lines all age with the heat, time and the environment and they will all require replacing.
My 1989 is due for hose replacements.
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From: San Jose
838dillon
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I'm having the same exact issue with my resonance solenoid, the is a loud ticking when key is on 2 position. car cranks but won't start. When I unplug the solenoid then the carbon canister vacum switch right below starts ticking. Then I unplug both ticking stops. I replaced both parts are the ticking continues. Please help.
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I'm having the same exact issue with my resonance solenoid, the is a loud ticking when key is on 2 position. car cranks but won't start. When I unplug the solenoid then the carbon canister vacum switch right below starts ticking. Then I unplug both ticking stops. I replaced both parts are the ticking continues. Please help.
