I have an AFB 4055S on otherwise stock 300. Car idles properly at around 750rpm in gear and close that in gear with a/c on and idle solenoid engaged. Problem is that with a/c on at idle, engine will load up and eventually die. No a/c everything works fine. On the highway, with a/c on, seems fine until you step down on it, then it sputters and acts like it swallowed something eventually clearing up and running ok. I have tried carb cleaner injected down vents and with car running, no change. Carb was rebuilt three years ago. Car gets frequent use, rarely sitting up for longer than a month. All this only happens with a/c on. Time for a rebuild?? If so who is the guru on AFB's? Oh yea, running with a/c is mandatory here in Louisiana, unless you like sticking to the seats. Thanks for any help.
Sounds like vapor lock from the increased temperature with the A/C on. How hot is it getting and is the exhaust crossover open? The intake can get so hot gasoline boils in the carburetor.
I had something similar. I have a 300 2bbl, auto all completely stock. Thought it was vapor lock too, also hard starting after it sat for a few days, sometimes when it was hot and shut off while getting gas. I installed a electric fuel pump with a switch under the dash to give it a boost after sitting awhile, just turned it on to get a good prime, then ran fine. Also on the freeway it would sometimes stumble like a vapor lock, hit the electric fuel pump switch a few seconds and it would straighten itself out. This went on for months. Finally replaced the old fuel pump on the engine and that took care of the starting problems and the freeway stumbling. Looks like it was the fuel pump all along.
Crossover for heat are blocked and filled. I wondered if it was vapor lock, but thought the return line system would eliminate that sort of problem. I will most likely put in an electric fuel pump to eliminate long cranking time after setting for a few weeks, if nothing else. Thanks for the input.
