Author Topic: Can't get fast idle to set.  (Read 360 times)

Offline drlance

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Can't get fast idle to set.
« on: July 09, 2019, 01:20:31 PM »
Hi all,

  It's been about 40 years since I last rebuilt or played with a Q-jet, so I am a little rusty.....

  I have a 1974 Corvette 350 with a quadrajet with a Divorced Choke, Carb# 7044208.  I have looked and cleaned and tried to adjust everything I can think of and the Fast Idle cam lever doesn't raise when you depress the gas pedal to set the choke., The choke plate closes and since I turned the curb idle up to 1000 rpm it will start ok and the choke plate does open after a few minutes of run time.  But then I am stuck with a permanent 1000 rpm idle. 
   i haven't been able to find a picture for the choke side of this carb to be certain all the rods are hooked up correctly.  Plus from what I can tell the Divorced choke was only used for a couple years....  Any ideas?   
  Thanks

Offline Cliff Ruggles

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Re: Can't get fast idle to set.
« Reply #1 on: July 10, 2019, 05:31:25 AM »
The 1974 Chevy carb uses two links, one to unload the choke and up to the secondary air flaps.

It also uses an assist spring on the pull-off to help set the choke and lift the heavy fast idle cam.

The cam should raise to it's highest position when the choke flap just reaches fully closed.  If not it isn't put together correctly or something is bent and out of adjustment.

This assumes that you have the part that raises the fast idle cam under it and not on top of it........Cliff

Offline drlance

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Re: Can't get fast idle to set.
« Reply #2 on: July 10, 2019, 09:39:23 AM »
Will try to stand on my head either tonight or tomorrow to see if the spring is even there, let alone where it is connected....  Thanks!

Offline Cliff Ruggles

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Re: Can't get fast idle to set.
« Reply #3 on: July 10, 2019, 10:16:05 AM »
The assist spring is on the pull-off and visible without standing on your head......

Offline drlance

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Re: Can't get fast idle to set.
« Reply #4 on: August 08, 2019, 12:35:53 PM »
After getting down low and looking at what was there, the coiled spring on the throttle shaft isn't hooked to anything.  I've tried it 3 different ways and it still won't lift the fast idle cam.  I guess I'll have to take the carb off the car and try to see what is going on.

  Cliff, is the 'standard' rebuild kit ok for this??  It's a bone stock 350 with 48K on it, but sat for about 7-8 years.

  I figure if it's off the car may as well freshen it up.....   Thanks!

Offline Cliff Ruggles

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Re: Can't get fast idle to set.
« Reply #5 on: August 09, 2019, 01:49:29 AM »
The SR kit will have everything in it to do a complete/correct rebuild.

Vacuum test the choke pull-off and replace it if it doesn't hold vacuum or releases too slowly....tks....Cliff

https://cliffshighperformance.com/Quadrajet-rebuild-kits-and-quadrajet-parts/quadrajet-rebuild-kit-sr