Guys im back again with a head scratcher. so my 65 pontiac bonneville with 4brl and Carter AFB carb is disturbing my peace and summer time cruising tranquility. it started by dying everytime i stopped. i got the carb back (i had removed it and delivered to shop). i put the carb back on and it still does the same thing: runs great when chokes on, but as soon as she’s warmed up, she’ll die. start-die, start-die. if you keep foot on gas, it runs and sounds great. i can sometimes cajole her into staying running for a minute or so while i look for leaks but thats it. What ive done: found and fixed leaks around carb base. looked for vacuum leaks in hoses, replaced dash-pot, reset timing to correct setting, attempted to raise idle. The raising idle one is the hardest. its DOESNT SEEM TO MATTER how much i loosen or tighten the idle screw, it doesn’t really affect the idle same with the rich/lean screws. I’ve been told Carter AFB idles are tricky, but man… Do you think it could be vacuum advance? I had some say check the “dwell”, and i will, but ive had other people say thats not it. it seems like a key clue that the idle screw doesn’t work to raise or lower idle, and its just been rebuilt. i was told that it was a clue that when i drive, it will die when i stop in drive AND in neutral. Also, idle doesn’t drop when i press brake, i was told if it did, that was a clue.
Is the choke fully open when it’s warmed up? Do you know anyone that knows carbs? I think a good hand could solve this quickly if they could get their hands on the car. I’m guessing some kind of linkage snafu. With some mis-adjustment thrown in on the side.
Questions. Is the business end of the base idle speed screw touching anything? If it is, the thing it’s attached to may be slipping on the throttle shaft.
Stallng when you step on the gas (Chevy experience) could be from a missing choke stove pipe or hose. You’re supposed to get some hot air all the time. The butterfly in the air cleaner intake snorkel should be closed on startup. It stays closed for only about 45 seconds; then the warm air closes or opens the plastic valve on the air cleaner housing causing the butterfly to open then you get the somewhat cooler air.
Stalling on stops could be related to no base idle. The screw might be too short from “unauthorized repair.” Then there may be frayed wiring in the distributor. Vacuum advance frays the wires by moving the breaker plate back and forth. I’ve only seen that on electronic ignition on Fords about 1985.
Also:Get a HOLLEY.
Yes, fully opened. carb masters are hard to find these days!
This site might help or at least give you some areas to check
I’d follow the troubleshooting checklist from that web site. Looks very thorough.
this one may apply:
Q: Why does my Carter AFB only idle with the choke closed?
A: This usually means the idle circuit is plugged or restricted. Cleaning the idle passages and jets should restore proper fuel flow.
also this:
2. Idle Mixture Screw Response
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Turn each idle screw in and out while running
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Engine changes = circuit working
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No change = plugged idle passage OR vacuum leak
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Hopefully, George will log in with some advice. IIRC, he has a lot of experience with carburetors.