928 at last

Hi,
Need a little help here. I've run the recommended diagnostics on the resonator flap operation.... vacuum good..Solenoid operational..."Flappy" free to move and responds to manual vacuum . Issue is that under load to 5,000rpm, there is no electrical signal to the solenoid to actuate the high speed flap position. Start-up test shows normal operation which would seem to indicate that the wires and vacuum lines are in working order. I'm guessing my key question is .....what system or sensor feeds the LH to tell it to actuate the resonator flap @ 4,500 rpm????
No, I haven't received a copy of the manuals yet, but they are on order......
Thx.
Rob.

928 at last

Sorry, should have mentioned that the throttle sensor seems to be working properly. At highway speed, a "foot off" results in an mpg reading of 90, and gentle application of the throttle after shows +/- 40 mpg.

Tom. M

You have to rev through 3500 with vigor..just accelerating up to 5000 without flooring it..won't do it...under the hood..start the car and then rev it really quick....it should flap... no reason not to if you are getting the start up flap..

Good luck

928 at last

OK...I took it up pretty quick...but not floored. How vigorous are we talking here?

Tom. M

I'm thinking you want to hit it..like rev to 5 or 6 k..and back ..in 1 or 2 seconds...sort of like blipping the throttle but taking it to 6k...

bigmac

My 90 S4 will flap at about 3500+ when floored from a start. Mac

928 at last

Thanks....I'm going to hook up a hard wire test circuit and take it out on the road. I'll keep you posted on the results.....
Regards,
Rob.

KenRudd

Rob,

What were your end results? I am looking at a flappy system where the vacuum part of it works perfectly, but the electrical seems suspect. Other posts on this topic seem to focus on just vacuum issues and gloss over an electrical failure , i.e, the solenoid is not getting the "signal".

-Ken Rudd

Ralph Newman

Rob, I had the same issue. The flappy would work at start up but not at higher rpms. Found the vacuum line was leaking. Had enough vacuum to overcome it at startup but not when you need it.
Good luck, Ralph

928 at last

Hi, Sorry all but I haven't had the time to do the hard wire test yet. (Summer holidays etc.) Will be soon though. Found some other issues in the interim (Anti-Knock sensor off-line) which really isn't helping.......
Ken, I'll post as soon as I run the test... Hopefully this weekend. Ralph, thanks! I thought that might have been part of the problem, so after I dothe circuit test on the solenoid, I'll recheck the vacuum.
Regards,
Rob.