Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Can’t Lower Idle

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Chevynation:
I’ve tried disconnecting the vacuum advance as well and the idle does drop but I still can’t kill the car with the curb idle screw. No booster, carb, or intake leak. I’m not familiar with the method you’re describing for testing for a vacuum leak. Where do I connect my gauge to perform this test besides the ported vacuum port to display zero vacuum while running? Thanks.

quadrajam:
This would be testing for leaks on the bottom sides of the intake gaskets that
are not accessible. You have to seal off the dipstick tube, oil fill hole, valve cover
breather hole and anything that exposes the crankcase to atmosphere.
I use that super sticky HVAC foil tape. degrease area before sticking it on.

Pull the PCV valve out of the valve cover and let it lay out of the way with
the hose still hooked up. The vacuum gauge kit usually comes with an adaptor
to connect it into the PCV grommet. otherwise you will have to get creative
with some fuel line and electrical tape. On a warm idling engine you should
see zero vacuum. not even a slight needle deflection negative.

Hopefully there will be no problem and you can tune it to compensate.

Chevynation:
Interesting, I’ll be sure to try that out and report my results back to you. Thanks.

Chevynation:
I covered the bypass ports and the idle did not drop any so I may have an internal vacuum leak. I left my gauge at home so I have to test for that tomorrow.

Cliff Ruggles:
"So I’m at 32 degrees at idle."

That much timing at idle will make it difficult to slow the idle speed down.......

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