Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Hunting at idle.

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slicer87:
 Yes I have, it seems that and the idle mixture jets are not affecting idle very much. I have replaced most of the emission hoses but I will spray carb cleaner to see if I have a vacuum leak somewhere. I am thinking that maybe the purge valve for the EVAP system is bad.

Cliff Ruggles:
Try this.  Find the best settings with the airbleed adj and idle mixture screws.  Gently "tip in" the choke flap, or place your hand over the choke housing.  Just richen it up slightly, don't choke it out.

See if idle quality improves.

Next, pull off a small manifold vacuum hose, and see what happens to idle quality.  Re-adjust the mixture screws and airbleed screw if/as needed.

Let us know what happens?....Cliff

slicer87:
I tried what you said Cliff and here is what happened. When I placed my hand over the choke housing the idle did improve. When I pulled off a vacuum hose to cause a leak there was no chage in idle quality. This is with the carb set at prelim settings, idle jets set at 3 3/8 turns and the idle air bleed set with the special gauge.

Cliff Ruggles:
If idle improved then you need more idle fuel, or less idle air, or both.

Those mixture screws are fine pitch metric threads with tiny holes under them.  Not uncommon to have to back them out 4-5 turns or more to get enough idle fuel. 

I would also turn the idle airbleed screw clockwise a bit and see if this helps?.....Cliff

slicer87:
 I was able to get the M/C dwell to stay in the 25 to 35 deg range but the engine will still not idle below 1000 RPM. It just stalls out immediately but it needs to idle at 650 RPM.   

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