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  1. #1

    Question STALLS COLD SURGES WARM AT SPEED How Come???

    STALLS COLD SURGES WARM AT SPEED How Come???

    When cold stalls while backing up first thing in the morning… sometimes stalls a little when warm after stop and first accelerating… when doing about 65mph, she surges as I lift off the throttle a little or give it light throttle. Does anyone have a good diagnosis and solution?

    It may be carburetor adjustments. I don’t think the automatic transmission is at fault.

    I replaced the ignition components: electronic control module, spark plugs and wires, distributor cap… also replaced PCV valve, air filter, vacuum hoses. The seal at the air filter housing of one vacuum hose may not be good.

    I replaced the fuel pump and fuel filter, plus installed a new second fuel filter.

    I thoroughly cleaned the carburetor 3 times, and installed a complete rebuild kit. I left old components on the carburetor like the automatic choke. I may not have set some screws exactly right such as fast idle, and 2 barrel idle. The carburetor components seem to move freely. But, I wonder if I need to sand or crocus cloth the tight pins.

  2. #2

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    Some more specific info would be helpful. I thought I recalled your nickname, and searched your past posts, and you are indeed the fellow who had great gobs of black goo in your Ford two-barrel. These are lean idle circuit issues. Tell me how the rebuild went, specifically how you cleaned out the idle feed restrictions at the bottom of the small idle tubes that are attached to the underside of the booster cluster... also, how did you initially set the idle mixture screws (lightly seated, and then how many turns out?), and then how were they adjusted once the engine was warmed up? They weren't? Adjusted warmed up is what counts, big time, and both to be the same number of turns out. Where are they set (how many turns out from lightly seated) right now?....
    Last edited by Walking-Tall; 02-10-2018 at 06:58 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  3. #3
    FEP Power Member dagenham's Avatar
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    Jul 2016
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    Duncannon PA
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    1,047

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    I'm with walking tall. But I recently bought an Edelbrock carb. The install manual warns to check Ford fuel pumps for fuel pressure. The carb may surge due to excessive fuel pressure. So as a last resort check your fuel pressure. Also, why and where do you have a second filter?

  4. #4
    FEP Senior Member 854vragtop's Avatar
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    Dec 2006
    Location
    Greensboro, NC
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    556

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    What type of carb do you have? I've had surges when cruising at steady state freeway speeds due to a lean condition when they started adding ethanol to the fuels. The stock primary jets were 62's when I was running my 4180c Holley 4 barrel. Bumping the jets up to 64's solved the surging problem.

    Surging can also be caused by an overly rich condition, such as when your choke is not completely open after the engine has warmed up. Is your choke open completely with the engine warm?

    Stalling when cold can be from a situation where your choke isn't closed enough. It can also be caused by accelerator pump linkage that isn't adjusted correctly. With your engine off, blip the throttle linkage and see if you get a stream of fuel from the squirters immediately. If you have any delay, you need to adjust your pump arm linkage (bolt/spring combo) so that the fuel squirts out with the slightest throttle movement. You must do this when the engine is warm and the choke is completely open and off the high idle detent. If you adjust the bolt spring combo with the choke on the high idle detent, you will get slack in the linkage when it comes off the detent (steps on the high idle cam) and this will delay the fuel leaving the accelerator pump squirters, causing a bog.

    Edit: Just saw that you have an Autolite 2V carb. I'm not sure how to adjust the accelerator pump linkage on that. Totally different than the Holley I mentioned above. Jets too small, choke operation, and any vacuum leaks may contribute to your problem though.
    Last edited by 854vragtop; 02-11-2018 at 09:43 AM.
    '85 Mustang convertible GT, 5 speed, 4V
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    '68 Mercury Cougar, w/ '88 5.0L, 4V
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  5. #5

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    Case in point of blocked or partially blocked idle feed restrictions:
    I have been and am working on the carburetor that belongs to just about as much factory hot rod money could buy from Ford in 1972, an R-code Mustang mach1, with solid lifter 351C "HO", top loader four speed, 3.91:1 rear gears in the nine inch, etc... it's rather odd, one-of-a-kind Autolite/Motorcraft 4300D spread bore four barrel carburetor. A historically typically troublesome carburetor. According to an article I read, 1 of only 336 (or 366?) such mach1's like this were produced... so for the rarity factor and such, it was decided to stick with the oddball carburetor... that I'll sort out. The point is, one of the (mentioned later, after I'd already seen the problem) issues was the general inability of the owner to get the car to idle... and most/many Autolite/Motorcraft carburetors have pickup tubes with idle feed restrictions in the ends of them like this carburetor does, like your carburetor does. Or in others, the restrictions are in angle passages in the booster cluster that then the idle air:fuel mixture heads down to the transfer slots and idle mixture screw ports. These pick up the fuel in order to idle with the idle circuit, and they are usually on the order of being quite tiny. These idle feed restrictions, seen below at the ends of the small inner tapered brass tubes, holes' measure 0.026". The problem in this case were small screen filters that had been installed incorrectly, too far, and were mostly or fully blocking any idle fuel from getting accessed for the car to idle. Hence other found issues like way cranked open primary idle speed, and idle mixture screws nearly four turns out, etc...

    The installed filter screen on the left is about where they can be or should be set. There's about 3/8" of space between the tube tips where the idle feed restrictions are and the floor of the carburetor... no need to ram the screens all the way. The installed filter screen on the right is pushed down against the end of the tube, blocking the idle feed restriction with the screen's folded and soldered end. IMHO, a dumb specified design provision. I understand their purpose of a little insurance of not letting debris into the idle circuit, but they aren't in anything else I've seen, and I think they're dumb because they open the opportunity to be installed incorrectly like this, causing a silly problem...






    ... and the ultimate point is, make sure your idle feed restrictions are clear, and do the same with all air bleeds and other feed restrictions and passages in the circuits while you're at it. If you removed the booster cluster when you disassembled and cleaned and rebuilt the carburetor, you'd have seen the tubes. A fine copper wire pulled from some strand wire and carefully inserted in each idle feed restriction and some cleaner and compressed air goes a long way to no-trouble function. Good luck with it.
    Last edited by Walking-Tall; 02-13-2018 at 10:40 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  6. #6

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    ^ 1972 R-code Mustang mach1 w/4300D carburetor owner says, "... it runs and idles very nice, thank you"
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

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