Mike C.

I just rebuilt the throttle body (Arnnworx kit), replaced the venituri o-ring and checked all vacuum lines/connections and I'm still getting a fast idle (around 1400 rpm according to the car's tach). I even unplugged the ground from the AC idle valve (AC was removed anyway). I tried to back off he idle with the throttle bypass screw but it doesn't seem to have much of an effect. Is the problem likely with the auxilliary air valve? (early '85 car)

bearone

check the basic setting for the throttle stop.

87951

sharky47

Went through this before - take the TB off the car - PITA, just do it.

Now, hold it up to the light and make sure the butterfly is centered. Now set the physical stop so that the valve is closed, but not jammed. Now set the TPS so that you hear a click when it closes EVERYTIME. Now reinstall and set the idle using the bypass valve when the car is at operating temperature.

Follow these steps by the letter - it's a pain after you have it all back together, but I have been there and this is the correct way to do it.

F18Rep

Dan... you da man. I guess I better put that "hold it up to the light" trick in the instructions. Sorry Mike... Bruce

Mike C.

I did all of that Dan. I checked under the hood after getting to work this morning (while idling at 1400) and the throttle was closed, TPS was engaged.

Mike C.

Out of curiosity, do any of you remember how many turns out your throttle bypass screw is set? Mine was at around 2 turns when I pulled the TB apart for rebuild.

Mike C.

Just tested the TPS with an ohm meter and it checked out O.K. ALso checked resistance on the aux air valve an it tested good too. Looking a little deeper into the aux air valve, the wiring diagram shows it as an on or off device (slaved to the fuel pump relay). When you look inside one of the ports on the AAV, it appears to be capable of variable open area, which would make sense if it were somehow regulating idle speed. But the wiring diagram shows it as an on/off device (open or closed) based on the fuel pump relay state. Near as I can tell the fuel pump is always on when the car is running so what is the point of having the AAV always full open? I just don't see how it regulates anything. Clarks doesn't have much to say on the little beastie - just that it may cause idle surge problems if not working. Mine idles steady but too fast....

Mike C.

Bump. O.K. so this isn't a hot topic. Anyone?

StoogeMoe

Here's a suggestion. Pinch off the vacuum line to the AAV and see if it changes the idle. If it does, then you know the AAV is at fault.

____________________________________
1986 944 NA - Guards Red - 91k miles - minty
1983 944 NA - Platinum metallic -11k mi beginning a new life
1985.1 944 NA - Guards Red - donor car
1984 911 Carrera Coupe - Guards Red (gone, but not forgotten)
"If you're not living on the edge, you're not living"

Mike C.

Yes, going to try that tonight. I also read that a bad TPS can cause a high idle and that sometimes they will test good when cold but fail when warmed up...

kgelles

sometimes the manifold gaskets can become old and crack. Any extra air that gets in around there can cause the problem you are describing. It's worth a quick glance just to be sure they are ok.

Mike C.

I had the intake off not too long ago to replace oil/air seperator o-rings so those gaskets are fresh. I did do the pinch hose test on the AAV and it made no change to idle speed. I assume that means it's either plugged up it was supposed to be closed (the wiring diagram seems to indicate otherwise). I also checked the TPS when hot and it still works properly. Finally, I tried closing down the idle bypass screw some more and was able to get the idle down to 950-1000 (according to car tach). We'll see how it holds up....