Having owned 5 Z cars up to this point, I am by no means new to the Z world. However, This little thing has got me stumped. What exactly is it? Anti-Backfire valve? I notice that it temporarily Keeps the throttle open after releasing the pedal. This leads me into my second question. After driving for extended periods (more than 5 minutes) at higher RPM's on the highway, my engine does not want to return to a low idle but instead hangs out around 1800-2200 RPM. Could this be the cause? I have watched the valve while opening the throttle to 3500 Rpms and it seems to work fine, keeping the throttle open just a few seconds. Any other Ideas? My carbs are tuned and my mixture isn't lean so i dont think that would be the problem....Im stumped.

 

If you haven't downloaded the free FSM yet, or bought a Haynes manual, I suggest doing so now.

XenonS30

According to my 240Z / 260Z Haynes manual, the part on the upper left of your circle is the "throttle opener control valve" and the part on the lower right of your circle is the "servo diaphragm". See Haynes manual page# 61.

 

that valve is for your AC , it brings the idle high if you have the AC on.

 

I saw that as well in the Haynes manual I have. However, I still cannot find a purpose for it. As for the A/C High Idle. The car does not And to my knowledge, never has had A/C. Regardless of what it does, I turned the valve completely shut and my high idle problem has been eliminated.