Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Q-Jet 17057274 idles too fast

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Cliff Ruggles:
All 4 throttle plates should be fully closed and very little light showing around them with the idle speed screw all the way backed out.

Correct this problem first, then you know if it's still running too fast (rpm's), then you have a vacuum leak someplace.....Cliff

beertracker:
The four throttle plates are fully closed and very little light around them with the idle speed screw all the way out.  New PCV, gromit and hose did not help.  I suppose the vacuum leak could be internal to the carb, carb base gasket, manifold gasket next to head, rusted through manifold or valley pan?

Carb has primary bushings & your rebuild kit installed.  I don't believe the secondary shaft is leaking air but how can I test;  water & soap spray bottle or propane test?

Is there something I should be looking at in your book? 

Thanks, bt

429bbf:
something has me thinking . you said in your first post that if you open the sec. flaps a little bit the engine slows down.correct me if im wrong but you would think that this would allow it to run a little faster if the lower plates were slightly open. if the plates are completly closed i dont see where it would change anything unless you were leaking on the lower bowl gasket.you dont have a spare carb to throw on to help solve the problem? iv got spares for people with problems i have them throw one on and if it fixes the problem then  i overhaul there carb . if not they have to look elseware like timing etc.f.w.i.w. dean

beertracker:
429bbf,  thanks for the suggestion.  I will look into a leaking bowl gasket as you mention.  Unfortunately I don't have a spare carb to try.   I may have to get one at the next swap meet.

I did measure the vacuum and it's 18-20 " Hg so low vacuum is not a problem.   Another idea, does this sound like too strong a power piston spring?  bt

beertracker:
Forgot to mention the carb is drilled for by pass air.  bt

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