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Old 01-12-2013, 07:55 PM
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Quadrajet Question

I was reading several articles online and got some conflicting answers.
The late model pre computer controlled Q-jets have the adjustable part throttle. A article I read says the APT also effects idle as by leaning it sets the metering rods further down in the jet. Well that doesn't make sense to me as the Q-jet, like all other street carbs have they're own idle circuit which is why they have idle mixture screws. What I'm dealing with is the Q-jet I have on my modified 4.3 V6. The idle is set low as it can go, in fact it's so low the idle speed adjustment screw isn't even touching it. It still idles higher than I'd like which is around 900 RPM. I've checked it high and low for vacuum leaks and there are none. I've also slowed down the spark timing from 24 degrees before top dead center to 18 degrees, that helped some but not much. I'm also positive the mechanical weights on the distributor isn't stuck or sticking open so I'm at the point to where I'm slightly confused on why it won't idle down. If the APT controls the idle any as the article states then I could just lower it's setting by lowering the metering rods further in the jets, but as far as I know they have no effect on the idle speed as I stated so I don't see that working.
Also I'll mention the throttle body on it is in great shape as it's already had the bushings replaced so any other ideas on why it won't idle down?
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