Got a question about the idle-up diaphragm on the Aisan carburetor.
What exactly is the purpose of this thing? I have had my truck for 6 or 7 years and it has never been connected to a vacuum port. With the adjustment screw down as far as it will go and vacuum applied, it idles the engine up to around 3000rpm, though it's possible that the original adjustment screw has been replaced with one that's too short.
Repair manuals are pretty vague about it and I can't see in the vacuum diagrams where it is supposed to be plugged in.
The fast idle cam does the job of kicking the carb to the proper fast-idle speed, so it seems that the "idle up diaphragm" is either redundant or just completely useless.
As always, everyone's replies are appreciated.