Hesitation off standstill , 1966 289

[Chaseman]

Hi , my Rustang has developed a bit of a quirk of hesitation off a standstill. But the odd thing is I can punch it all I want once I'm moving and it doesn't hesitate it just takes off as usual. Also again this is trying to get moving when it hesitates , it does fine at anything above 20 mph.

Thanks
Chaseman

[fordman]

that is the accelorator pumpin the carb going bad. they work fine once they get going. but will hesitate when you start from a stop.

[Chaseman]

oh man my dad just rebuilt it as a B-day present , is there a way I can check? Also let me better explain my hesitation , It is more severe when I try to gently pull from a stop and happens less when I jump from a start. Could it be dwell or timing , my dizzy came loose and thought that was the reason for my hesitation ( it was way retarded) but when I turn the timing high enough to make the hesitation go away , I get bad detonation during when I give it gas in third at anything below 35-40 course that could be of my tranny's dislike of downshifting automatically.

[fordman]

well then maybe it isnt that accelorator pump then. if it done it at a high stomp from a stand still it woudl still hesitate. somaybe it is the timing or a spark related issue.

[Chaseman]

Oh! Yes that makes sense , I've checked my Brake booster hose but I completely forgot about the vacuum modulator. Thank You!

[VirginiaCityFord]

You can also take some carb cleaner or Berryman's b12 and squirt it around the carb and intake. If there is a vacumum leak that you can't see it will suck in the chemical and the idle will temporarily rise

[mjhaltom]

Vacuum advance gone bad?

[TNIceWolf]

Try checking for a broken or loose engine mount. That allows the fuel in the bowl to slosh around.....causing a stumble under load......... its not under as much load at speed.