Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Idle too high

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tazjamin:
i rebuilt my carb while going through your book. this is my first carb rebuild too. i at first thought i did a great job it ran perfect no problem but the idle screws were all the way in but the idle was perfect and it ran good. then i did a tune up on my car and from there i have been having issues. I got to say first i haven't been able to time the engine yet because i have been waiting on a new timing tab for some reason mine is gone. That will happen tomorrow since i just got it in the mail. now i have had the engine running and it seems to run a lot smoother and more responsive but my idle is at 1800, everyone has been telling me it's my timing but even as i wait i can adjust the timing a little and it still stays there i may be able to get it to 1200 but thats it and its about to stall. i have a feeling that its something i did to the carb and once i get the timing right i would like to know of what could be wrong with the carb. the carb i got a rebuild kit from jet performance i also know its a 79 Oldsmobile carb please can anyone help me the only mods i did was drill holes for idle bypass air, adjusted the throttle plates to 90 degrees, brass float, and secondary air flaps notched. I was pretty happy when i did all those because they looked like how it was done in the book but maybe i didn't do enough mods or too much but any help would be great thanks. i plan on timing the engine tomorrow morning and hopefully figuring this out

Cliff Ruggles:
Big vacuum leak someplace?

Stock cam or aftermarket installed?.....Cliff

tazjamin:
stock cam

tazjamin:
i found out that the choke wouldn't disengage all the way and was keeping it reved up too high now i can adjust it with the idle screws i just haven't been able to find out how to fix that yet

beertracker:
I had a fast idle problem with my pontiac 400 & qjet.  It would idle at 1400 rpm or higher.  Eventually I discovered the problem.  The secondary return spring had lost strength over the years and the secondary throttle plates were not closing fully.  This allowed a air leak past the secondary throttle plates.  To solve this I re-bent the secondary return spring so it had more closure force.  Problem solved and my engine now idles at 750 rpm.  Hope this helps.

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