Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Warm idle fluctuation with slight backfire [VIDEO]
Cliff Ruggles:
They made those carburetors with and without the limit or rich stop. If it's up against the IAB's valve and pushing it to the deepest position you still should be able to use the adjustment it the airhorn keep the idle from being unstable.
Do you have full control with the idle bleed adjustment in the airhorn?.....Cliff
turboguard:
--- Quote from: Cliff Ruggles on January 28, 2017, 02:39:33 PM ---They made those carburetors with and without the limit or rich stop. If it's up against the IAB's valve and pushing it to the deepest position you still should be able to use the adjustment it the airhorn keep the idle from being unstable.
Do you have full control with the idle bleed adjustment in the airhorn?.....Cliff
--- End quote ---
So after I drove home (~30 min) today I hopped out and immediately hooked up my dwell meter...with the IAB valve screwed all the way in to about 1 turn out, it idles the highest and smoothest (but still stumbles and backfires slightly), but the dwell is pegged at 54°. Once I start backing it out, the idle drops slightly and starts stumbling and the dwell goes down into the 40's and slowly decreases as I unscrew it. I can unscrew it to the point where I hear the piston stop hitting the IAB valve's rod and actually tick on the airhorn itself and the dwell is in the 30's. I have the idle mixture screws at about 3 1/2 turns out during this, and the lean stop screw set approx. 1.304 inches according to the guide.
I'm kind of at a loss as to how to get it running perfectly without scrapping the whole thing honestly, lol.
Cliff Ruggles:
3.5 turns out from seated is pretty lean with one of those carbs as the mixture screws have metric threads. Most end up 5-6 turns out from seated to get enough fuel to them to idle well.
I would install the correct airhorn if doing it here as I like having the limit for the metering rods so we can fine tune them to run well if the M/C solenoid quits working. We probably have a dozen of them in the core pile.....Cliff
turboguard:
--- Quote from: Cliff Ruggles on January 29, 2017, 03:28:13 AM ---3.5 turns out from seated is pretty lean with one of those carbs as the mixture screws have metric threads. Most end up 5-6 turns out from seated to get enough fuel to them to idle well.
I would install the correct airhorn if doing it here as I like having the limit for the metering rods so we can fine tune them to run well if the M/C solenoid quits working. We probably have a dozen of them in the core pile.....Cliff
--- End quote ---
How much would you charge for a good airhorn? I think my best bet is getting the appropriate airhorn so I can better tweak the settings, plus my airhorn is slightly warped anyway so that's probably causing some issues too (although I am using the thicker gasket you sent which is probably helping a lot).
Cliff Ruggles:
We sell those for $15 plus shipping. We're here 8am-4pm, M-F EST...tks....Cliff
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