How does idle adjustment work on 3.2?

hobieboy · 08-10-2006, 07:06 PM

Hi,
Does anyone know how does the idle speed adjustment "screw" actually work on the 3.2 intake?

On the one I got, the "screw" is below the butterfly. According to Haynes (yes - that's the best I could find

), that is the adjustment screw. By turning it, I'm supposed to be able to adjust the idle speed.

But... when I look at it closer, it looks like a screw with a O-ring near the head. As soon as you insert it into the threaded hole, it will block all air flow, so tightening it deeper/shallower should not make any difference in term of letting air (or no air) in.

So, am I missing something? Or, is this not what the original 3.2 throttle body has?

thanks.

hobieboy · 08-11-2006, 05:23 AM

Nobody has any clue?

Does anyone at least know which way to turn the screw to up the idle speed?

thanks.

MattAlpha · MattAlpha's Garage

hobieboy,
I also have the Haynes manual as well as the Bentley manual and Wayne's books. The only one that I've found is the Haynes manual (under the updated/supplement section on later models) that speaks about adjusting the idle. I haven't done it yet and unfortunately the manual is very vague about how to actually accomplish the adjustment. I need to do it as well because my P-car idles at 650 rpm, but I'm not sure if you can use the rpm gauge in your dash for the adjustment because you're supposed to have a handheld tach that you "plug-in" to the engine.

My advice is to go ahead and try it. Get the engine up to operating temperature. "plug-in" your handheld tach and see where your engine is actually at. If its not idling at 800 rpm, then jumper the connections B and C in the test jack to stop the idle volumetric control. Turn that screw on the throttle body one way a bit and pull the jumper to see the affect.

Please let us know your results once you have finished.

-Matt

yelcab1 · 08-11-2006, 06:27 AM

The manuals are vague because you are not supposed to touch it. It is done at the factory and they they cover it up. After that the DME brain takes over and adjust the ignition, RPM, fuel, air etc so that the RPM is within range, the O2 is within range. If you have problem with idling, then you may have a vaccum leak. Also check out your accelerator linkage, cable, ....

No real harm done in adjusting that little screw under the yellow cap, but do remember where you start from so you can set it back if it does not work.

charleskieffner · 08-11-2006, 07:27 AM

someone in cars previous life had removed plug and played with it. when we had problems we tried to adjust. no adjustment..............nothing screw in or screw out. replaced it. and now it works.

jimi_c · 08-11-2006, 07:43 AM

I seem to remember that there's a description on the steve w sight - when installing his chips on the 3.2 sometimes you need to adjust the idle - you need to use a jumper wire in a test socket to do it properly, so it's not just turning a screw - look here:

http://www.911chips.com/dmeconvr.htm

hobieboy · 08-11-2006, 09:22 AM

Thanks for the input guys...

I'm actually not really running a 3.2 Carrera - I'm using the intake for my 930 EFI conversion. The reason for the question is: I think I need to adjust my idle air supply hence looking at this.

I actually just took the screw out from the throttle body. Looking at it, I still don't get how it can control amount of air going into the throttle body. May be I need to dismantle more to figure it out

avt007 · avt007's Garage

The screw doesn't let air in from outside the throttle body, it allows air to bypass the throttle valve through an internal passage. Screwed all the way in, it blocks off the passage= low idle. Screw it out= increased idle. On mine the DME must limit the top end, because my idle will not go above 900 or so. HTH

hobieboy · 08-11-2006, 10:58 AM

Thanks for shedding some light on this avt007 - kinda what I suspected.