Fast idle adjustment
Thread Starter
Burning Brakes
Joined: Dec 2021
Posts: 805
Likes: 260
Fast idle adjustment
Hi all .. I rebuilt my 75 manual Q-Jet and it is running beautiful . I set the fast idle screw which is located behind the choke linkage to1600 at cold start per factory emission sticker . However reading Lars Book on carburetor rebuild in says set fast idle at 1200… any opinions thanks
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
- I don't have a book about rebuilding carburetors.
- I don't recommend 1200 for cold fast idle: this can be a hair low on some automatic cars when dropped into gear. I suggest 1250-1350 in neutral, with 1270 as a recommended good target number. All the carbs I build are set up and delivered with cold fast idle set to 1270.
- You can set the cold fast idle to any rpm that produces a stable, reliable, and comfortable idle speed on your engine. I caution against excessively high fast idle speed since this produces unnecessary wear and tear on a cold automatic transmission when it is dropped into gear with high rpm and low fluid temperature. For this reason, I do not recommend the 1600 rpm cold fast idle spec.
Last edited by lars; Apr 14, 2022 at 11:00 AM.
