I have these symptoms with my car.
Twin SU-HS4 with over-run valves on th butterflys. Waxstat jets, proper
heat sheald. No vachume leaks or spindel linkage leakage, well sealing
butterfly's, in good running order.
Vachume is I guess somwhere about 21-23 in/hg, not shure about he
calibration.
Normal opperating temperature, and conditions.
Choke in fully.
The car idles at 1200 -1600 rpm, blip the throughtle and it returns to the
600-800 I set it at, and stays there untill.
You rev the engin slowly and it goes back to 1200 to 1600 rpm.
If you blip it realy realy quick so it cant pick up revs, the vachume is
lost, and it stalls.
So when it was doing this I opened up the bonnet, and took a look inside.
I first of checked the jets were at the correct hight, there fine.
I then tryed to close up the butterflys by hand, dosent drop.
I then tookt the adjust screws right up, and forced the butterflys closed
even more, they moved but the revs didn't drop.
This is why I think it's a sticking over-run valve, when you blip the engin
you start to draw a fast air flow, and then you cut off the supply of air
extreamly quick because of this it creates an inital vachume that is enough
to re-seat the over-run valve pining them open and snapping them shut.
How do I start to get the over-run valves to keep there mouths shut? It's
not like I can take them out, or anything like that!
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