Idle Speed Won't Adjust
 

Need some help. Idle is running low - around 500 rpm. Ran a jumper between B and C of the test port to adjust it; idle runs around 800 rpm with the jumper. Remove the jumper - back to 500.

If I play with the idle valve adjustment to bring the idle up without the jumper, as it's approaching 750 it starts to whistle; assuming that's not preferred.

Thanks!

You should play with idle adjustment on throttle only when jumping B and C. Do not try to adjust when the jumper is removed.
If you manage to get 800 rpm with the jumper, then keep this adjustment, remove jumper, and check the ICV itself or its control from ECM/Motronic. Something is probably wrong on this side.

Thanks wazzz. Will give it a try

What happens is you adjust the idle with the jumper removed? Just curious.

Hi Nick. As stated, “If I play with the idle valve adjustment to bring the idle up without the jumper, as it's approaching 750 it starts to whistle; assuming that's not preferred.”

Jumper removed means the ICV is auto adjusting the idle to nominal rpm (800 or so, depending on model year).

Assuming the ICV and its control are functional, which may not be the case here, the control (Motronic) will try to compensate the adjustment to maintain the nominal rpm, up to the point it cannot do it anymore because things become out of range.

Also, you can do the simple checks described in post #20 here:
http://forums.pelicanparts.com/porsche-911-technical-forum/360766-bench-testing-carrera-idle-control-valve-3.html

Thanks again, wazzz.

Question: Can you jump B & C with the engine running, or do you need to shut down every time?

Hmm good question. Not sure, but yes you probably can install and remove jumper between B and C while engine is running, since the status of idle and WOT switches is regularly checked by the processor and not only at startup.
Jumping B and C is the same as closing the WOT switch while the idle switch is also closed, which normally should never happen since you can never be both running at idle and running at full engine speed. This combination of peculiar switch statuses directs the processor to no longer regulate/control the idle speed. That's when you can adjust idle speed at nominal rpm.