With all other adjustments properly set up it will make a hiss as you describe. Crank the adjuster in - the hiss will get louder and you will end up with a low, lumpy idle. Crank it out to wide open - the hiss goes away and you end up with a high, hunting idle. In the mid range you should have a smooth 650-700 rpm idle with some hissing which will not be heard when you connect the feed line from the air box to the idle air manifold.Semi-related question about the "can of worms" junction. SHould it "hiss" at all like it has an air leak. Not sure if it is a sucking air leak or an over pressure air leak but mine hisses. Is that right or does it need to be tightened, gasketed, or otherwise readjusted to stop that.
In essence, yes. But the stop screw must be at factory specs to get the "delta" correct between the short and long rods for tuning purposes. For an AC compressor load, I suppose you could install a high-idle solenoid like some carb'd cars had back in the 70s.@Roadtrip: having read much of your and others' online writings, isn't the idle stop screw position critical only for setting the initial (baseline) relationship between the fuel pump long rod and throttle butterflies? After it is set with the "tool" or equivalent device, isn't changing its protrusion just akin to nudging the gas pedal or pulling the throttle lever? I.e., a tweaked idle screw should do no harm as the air fuel ratio will still be valid for the given throttle opening. With a larger than "baseline" protrusion, it may help nudge the idle speed higher to accommodate, say, use of an A/C compressor.
Well, I guess it's mainly that it feels lower than it used to be. I get some vibration when I sit at idle, which I didn't used to.What do you call "low?" 600-900 rpm is the spec.
You might check the timing. Also, check the plug color for mixture.