Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Idling Too High
Cliff Ruggles:
Is the Vacuum Advance adding timing at idle with manifold vacuum?......
Zach:
--- Quote from: Cliff Ruggles on March 12, 2023, 03:01:07 PM ---Is the Vacuum Advance adding timing at idle with manifold vacuum?......
--- End quote ---
I quickly checked this one so I could’ve done it wrong but unhooking and plugging the vacuum lines to the vacuum advance causes no change in idle. I could try a different vacuum source and skip the emissions check valve. Think I read somewhere that the check valve emissions equipment on a 77 trans am is timed and acts as ported.
Zach:
Still haven’t found a solution, there is an oddity that it will run at 800 rpm but I can’t reproduce this and it eventually builds rpm to stick at 1k, I’m wondering if it’s a distributer issue or the vacuum advance is sticking.
Currently fighting below freezing temps, might postpone this until summer.
Cliff Ruggles:
Check the timing when the problem occurs and make sure it's back to the "base" setting. Sticking distributor weighst or mechanical advance will cause exactly what you are seeing.....
Zach:
--- Quote from: Cliff Ruggles on March 21, 2023, 05:19:32 PM ---Check the timing when the problem occurs and make sure it's back to the "base" setting. Sticking distributor weighst or mechanical advance will cause exactly what you are seeing.....
--- End quote ---
I believe I solved the issue, early on it was vacuum leaks, timing, and improper tuning. I got the recommendation for a second tach, used a fancy timing light. Seems to be running at factory spec, my dash tach seems to be off by about 300. Makes sense why I’d see <800 sometimes. Carb is idling great, never heard the car at low rpm’s or knew what to compare it too, not very experienced. Appreciate the base plate rebuild, your book I bought helped a lot when rebuilding the main body, huge help Cliff.
Appreciate the help, seems to be solved!
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