My 66 Mustang boggs in the morning when starting but fine when it's warm

ford
mustang

#1

I’ve posted on a Mustang forum about my 66 Mustang bogging when I first start but when it warms up after 5 minutes, it runs great. I"m running a Holley Carb electric choke. The one reply that I thought was a good one was:



Where is your choke + wire hooked to? STA (stator) post on the alt.? If it’s wired somewhere else you’re probably getting 12V instant when you start up and the choke opens immediately so it doesn’t do it’s job.



Take the air cleaner off and have someone turn the key on (may not need to start) and see if the choke starts opening. The STA only gives 6-8V if I remember right so it slowly heats up the choke spring so it takes 5-10min. to be fully open depending on temp.



See if the choke is actually almost closed when cold, you may need to clock the choke cap as mentioned to get it set right and then test to see that it’s fully open when engine is up to temp.



Just trying to see if I would get the same reply as his and maybe I might’ve figured out the problem.


#2

FORGET connecting it to the stator post on the alternator…Electric chokes do NOT heat up and open instantly. They take a few minutes to fully open. 1966 model cars never started cold and drove off smoothly like today’s fuel injected marvels. A five minute warm-up was standard procedure…If your non-stock Holly carb is working that well, I would not mess with it…

An ace carburetor mechanic could probably adjust the choke tension and the vacuum pull-off distance and achieve nirvana, but it takes a lot of time, skill and patience to do it…You could try increasing the choke closed tension JUST A HAIR to achieve a slightly richer warm-up period, but you risk flooding on very cold mornings…

On a street engine, the 2 and 4V Autolite carbs worked much better than the leaky, cantankerous Holly’s…


#3

Is this an Ford OEM Holley on the car or an aftermarket Holley?

If it’s the Ford OEM carburetor you might check the choke pull-off diphragm. This pod is designed to pop the choke open about 1/8" when the engine first starts. If it does not the engine can load up, stumble, not want to idle, and possibly belch some smoke.

With the choke cold and closed apply vacuum (tester or attach a vacuum hose). The choke should pop open about 1/8" and stay that way as long as vacuum is applied.
Choke pull-off pod failures can be common with age on any carbureted engine.


#4

I was told by my neighbor that his 33 Coupe does the same thing in the morning like mine does and runs fine afterwards. That’s why I thought about not even touching anything since it seems to run fine after 5 minutes or so.


#5

This is an aftermarket Holley 600 carb. I had someone else on the forum say it was normal too so I’m getting the impression like CAddyman says, maybe adjust it slightly or not adjust it at all.


#6

Welcome to the world of '60’s cars. Carbed motors with electric chokes commonly acted just this way. Can you tell if you are getting too much, black smoke out the tailpipe; or too little gas? Too little means a quick couple of pushes on the gas petal uses the accelerator pump on the carb to feed the gas you need to aviod the stumble.

Most electric carbs can be adjusted. You should see a black plastic “cap” with a pointer and some marks on the adjacent metal mounting housing. You can loosen the “cap” and play around with different marks on the housing to see if you can improve the warm up performance.

On cars of this era I installed a manual choke a few times because the electric chokes just couldn’t be adjusted to work properly. Play with it, but pretty much all cars of this era didn’t run smoothly until they were warmed up. The goal was to keep them from stalling multiple times, a stubble without a stall was considered acceptable. Almost every car would stall at least once on the typical warm up cycle.


#7

There’s definitely no smoke and when I first crank it, the car starts at around 1500 idling. When I warm it up a couple minutes, I attempt to drive which it is about to stall. I try to give it gas and sometimes it would stay on ir the car stalls at take off. For the next couple stops, I try to take off and when I give it gas, it sputters a bit and then drives. Once I see the gauge rise just past the cold mark on the gauge, it drives fine. So does it sound like I’m not getting enough gas?


#8

My gosh, man. Give your Mustang a break. It’s old. I’m old myself and I don’t motivate very fast in the morning either.
I converted a couple of my automatic choke cars to a manual choke back in the 1960’s. I know that you won’t have the original equipment appearance, but IMHO the hand choke works much better.


#9

Take off the top of the aircleaner and see if the choke is open when you’re having this stalling condition. If it is, it’s opening a bit too soon (which would be my guess). Getting it adjusted ‘just right’ can take a lot of work, as described by Caddyman.


#10

It’s old with a rebuilt high performanced 289? Give ME a break hah. It only has less than a 100 miles on it. I finally found the downside after buying the electric carb. Made the mistake of taking JEGS advice.


#11

If push comes to shove and the carb keeps driving me nuts, I might get a manual choke one.


#12

Yep, sounds like it is running a bit lean when cold. The technique to quickly tap the gas petal 2 or 3 times rapidly, pushing about 1 inche per tap. That shoots in some extra gas to the carb via the accelerator pump. When you do this if the engine takes off and keeps running that confirms it is running lean and needs some more gas until it warms up some more.


#13

Yea. On the mustang forum, some guy said the same thing and it should be opening slowly. I’ll have to check that out. I might try to do the quick couple taps on the gas and see if that works. If not, then I have to get technical with it. Thanks!


#14

I’m gonna give it a try first. It definitely indicates there is not enough fuel going in at start. I’ll try the couple pumps on the pedal. Thanks!


#15

Jegs and others list manual choke conversion kits for Holleys, about $30.


#16

I agree with everyone that it’s likely carb/choke related, however, don’t over look the heat riser.

The heat riser is the passage way in the intake manifold that allows hot exhaust gases to circulate around the base of the carburetor. Those passages on some V8’s tended to plug up easier than others - causing drive-ability problems. Ford wasn’t one of them that was prone to plugging, but at least make sure that the cast iron around the base of the carb gets warm fairly quickly.


#17

This “rebuilt engine” is a key piece of information as now we have the possibility of an installation error with some component other than the choke.

I had a small block with the 600 cfm Edlebrock and an electric choke, no cold start issues whatsoever, so my point is cold starting/stumbling issues are not locked to carbs with electric chokes, it does not have to be this way.