Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Q-Jet 17057274 idles too fast
beertracker:
A couple of posts above I mentioned V cuts in the throttle plates. After closer examination it appears these are factory made. They cover the throttle shaft and are not a source of air passage.
I installed bushings and the fast idle continues however all play in the throttle shaft is gone.
Before and after the bushing work I noticed a tiny air gap about 1/32" uniformly spaced around the throttle plate and carb bore. I centered the plates within the bore so the tiny air gap is uniform this is with the throttle fully closed. Is this air gap normal?
With throttle fully closed and idle speed screw even with carb casting there is a small air gap of 1/16 to 1/8" of an inch. This idle speed screw is not touching the throttle and not adding speed to the engine.
Thanks,
BT
Cliff Ruggles:
All of the throttle plates should be tightly closed. If not, something on the linkage end is holding them open.
This accounts for the lack of control of the idle speed with the curb idle screw when the carb is in service.
It's actually a common problem, and requires bending a few items on the throttle linkage to get the plates to fully close, and open to exactly 90 degrees at full throttle.
There should be very little light visible around all the throttle plates when closed, if not, it still needs adjustments before being placed in service.....Cliff
rhino33:
It's actually a common problem, and requires bending a few items on the throttle linkage to get the plates to fully close, and open to exactly 90 degrees at full throttle.
what are these few items that need to be bent?
slicer87:
^ I think my Qjet has that problem.
beertracker:
I have been working on other things and today I got back to this problem. Still idles too fast. I found a vacuum leak in the power brake booster but plugging this did not help. All vacuum lines have been removed and plugged at the source. Could I have a internal vacuum leak in the Q-jet? If so how would I debug this?
The other leak possibilites I can think of would be manifold runner, manifold to carb base or manifold to head. I have a new PCV gromit so I don't think a PCV leak the is the cause. Running out of ideas.
bt
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