351C-2v having trouble running..

My 351C had been running great until winter hit.. It'll start up fine, but once I get it started, it'll idle for a good minute, but then it starts to "Surge".. *VROOM..dies down..VROOM..dies down..VROOM*.. and when it surges, it starts to get quieter, and finally stops running. I honestly dont know where to go to start looking for problems at this point:

What I've done to try and fix the problem:

• Replaced the Electric Choke with a new manual choke on my stock carburetor.
• Replaced fuel filter with a brand new one.
• Sprayed Carb Cleaner around areas for a possible vaccum leak.
• Had the carburetor rebuilt.

Any ideas at all? In my opinion it sounds like it might be a fuel pressure problem like its starving for gas in idle... Is that impossible?

Thanks a bunch!
Cameron

Does it do the exact same thing after you put a manual choke on it? What year and model?

It's a 1971 Mustang Grande. The reason I put a manual choke on was because the old electric choke would kick on.. but wouldnt turn itself off. But to answer your question, yes, it does the exact same thing with the Manual choke as well.

Your carburetor is a 2150 2V. It had a fairly complicated choke system(s) on it. From your first description, it sounded as if the fast idle was coming off as designed, but the choke pull-off feature was not opening the choke blade soon enough so that it will idle overly rich and naturally cut off.

Does the choke changeover kit you used have a fast idle feature also? When she starts cold and stabilizes, push the cable in enough to slightly open the choke blade but keep the fast idle up. See if she will idle that way for a full minute.

I'm not so sure the choke is the problem. But the only reason I say that is since it surges like that, its almost as if its not getting enough fuel pressure. But yes, I have tried the choke at all positions, midway in, all the way out, fully choked, all with the same results.. Thats the only thing I can adjust with the kit I got is the Line and Knob to adjust the choke... So it doesnt have a fast idle feature.

If the manual choke changeover kit has no fast idle then it is of little use.

My manual choke works great and does what it needs to. What used to happen with my electric choke was that it would finally kick on, but wouldnt kick off when I would accelerate.. I just honestly cant figure out what would cause it to act this way.

Maybe I am confused as to what you are saying about "Fast Idle".. Because all I know about the Manual Choke I put on as well with any other choke is that it opens and closes the valve for intake. What is the "Fast Idle"?

When a carbureted engine is started cold and/or is in cold ambient air temperature, the gasoline has a tendency to fall out of suspension in the fuel mixture in the intake until engine heat can warm the mixture. This is the reason for the choke blade, to deliver more gasoline and less air. The engine also has to idle faster than normal curb idle to also allow the mixture to reach the cylinders before the fuel mixture has a chance to separate. This is called fast idle. Once the choke is open fully, this feature will end and it goes back to curb idle.

When you close the choke blade on a mechanical choke, it should also increase base idle.

Oh, I see what you are saying. I believe the Fast-Idle Feature happens inside the carburetor but doesn't have anything to do with the manual choke I put on. When the choke is in and the blade is shut, the "switch" flips and increases the idle. Sorry for the confusion about that..

But I was wondering if it is just lack of fuel volume in the Float Bowl. There is an adjustment to allow how much fuel is left in the float bowl, and I think my problem might be is that that setting is too low.. causing all of the fuel to run out, *get quiet* and the the fuel-pump kicks in and it revs back up... Thus causing my surging. I think its either the volume adjustment in the float bowl, or my 2nd guess is that I dont have enough fuel pressure. Probably the 1st one.. What do you think?