460 Stumbling while cold
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From: Flaherty, KY
460 Stumbling while cold
I have an 85 F250 with 460 and T19. I recently rebuilt the carb and replaced the timing chain with an EFI set. Truck runs 100% better and my gas mileage has gone from 8 mpg to 12. Previous owner had the idle mixture screws turned practically all the way out, so it belched black smoke at idle, but now purrs like a kitten.
The only oddity that I have right now is that when the truck is started after sitting overnight, I have trouble taking off until it warms up. When I put a load on the engine it wants to sputter and die. If I rev it up real good and slip the clutch a fair bit to take off in 2nd, it'll go like it should. When it's warmed up this is never a problem, I can pretty much dump the clutch in 2nd gear without killing it, even taking off in 3rd is doable.
Not sure what the problem is here, but the choke seems to work as does the fast idle when started cold. Hit the gas and it immediately kicks down to idle speed. At idle (even when cold) there are no signs of hesitation until I release the clutch in gear. Please help me figure this one out!
The only oddity that I have right now is that when the truck is started after sitting overnight, I have trouble taking off until it warms up. When I put a load on the engine it wants to sputter and die. If I rev it up real good and slip the clutch a fair bit to take off in 2nd, it'll go like it should. When it's warmed up this is never a problem, I can pretty much dump the clutch in 2nd gear without killing it, even taking off in 3rd is doable.
Not sure what the problem is here, but the choke seems to work as does the fast idle when started cold. Hit the gas and it immediately kicks down to idle speed. At idle (even when cold) there are no signs of hesitation until I release the clutch in gear. Please help me figure this one out!
pedant
Joined: Jan 2008
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From: EXTREME southwest CT
A) it should be adjusted so it remains on the fast idle cam until it is 'half' warm.
B) sounds like the choke needs to be a little richer. If it is stumbling when cold now, wait for the middle of winter.
If too lean it may idle fine, but will not operate under load.
Have you set the choke opening and pulloff to spec?
What kind of gauge did you use? A drill bit?
B) sounds like the choke needs to be a little richer. If it is stumbling when cold now, wait for the middle of winter.
If too lean it may idle fine, but will not operate under load.
Have you set the choke opening and pulloff to spec?
What kind of gauge did you use? A drill bit?
Thread Starter
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Senior User
Joined: May 2013
Posts: 327
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From: Flaherty, KY
A) it should be adjusted so it remains on the fast idle cam until it is 'half' warm.
B) sounds like the choke needs to be a little richer. If it is stumbling when cold now, wait for the middle of winter.
If too lean it may idle fine, but will not operate under load.
Have you set the choke opening and pulloff to spec?
What kind of gauge did you use? A drill bit?
B) sounds like the choke needs to be a little richer. If it is stumbling when cold now, wait for the middle of winter.
If too lean it may idle fine, but will not operate under load.
Have you set the choke opening and pulloff to spec?
What kind of gauge did you use? A drill bit?
I'll double check the mixture screws; it's possible it may be too lean, I wasn't too precise when I first set them.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
No, if it idles and runs well when warm leave the screws alone.
You adjust the pulloff by bending the link,
You adjust the fast idle cam by bending the tab.
You adjust the closing by turning the thermostatic housing.
You adjust the pulloff by bending the link,
You adjust the fast idle cam by bending the tab.
You adjust the closing by turning the thermostatic housing.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Here's the Holley manual explaining the adjustments;
http://www.holley.com/data/Products/...9R10060rev.pdf
http://www.holley.com/data/Products/...9R10060rev.pdf
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
If you still have the conical breakaway screws on the choke housing it is long past time for a rebuild.
Use a Dremel with a cutoff disc or similar tool to make slots for a screwdriver.
Bring one of the three screws to a hardware store to match them for length and pitch.
You can use phillips or allen head to replace them.
Use a Dremel with a cutoff disc or similar tool to make slots for a screwdriver.
Bring one of the three screws to a hardware store to match them for length and pitch.
You can use phillips or allen head to replace them.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Oh, and Holley screwed up the bit about the secondary stop.
Adjust it no more than 3/4 of a turn from fully closed.
Adjust it no more than 3/4 of a turn from fully closed.
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Senior User
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From: Flaherty, KY
Thanks for the link, that helps a bunch.
The choke setting is non adjustable on this carb, this is one of the later variants with no index marks or way to adjust it.
I will check / set the other adjustments and see what happens.
The choke setting is non adjustable on this carb, this is one of the later variants with no index marks or way to adjust it.
I will check / set the other adjustments and see what happens.
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Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
First thing to check is if the choke butterfly closes when it's cold?
The choke spring housing on my 1987 4180 is / was not adjustable without modification.
Originally it had a tab that fits into a slot and to make it adjustable it would be necessary to pull the housing cover and grind the tab flush, then it would be possible to rotate the choke spring housing to adjust the choke.
Otherwise it might be worthwhile to double-check all the choke linkages to make sure they are correct, and also that the choke pull-off isn't somehow hanging you up.
The choke spring housing on my 1987 4180 is / was not adjustable without modification.
Originally it had a tab that fits into a slot and to make it adjustable it would be necessary to pull the housing cover and grind the tab flush, then it would be possible to rotate the choke spring housing to adjust the choke.
Otherwise it might be worthwhile to double-check all the choke linkages to make sure they are correct, and also that the choke pull-off isn't somehow hanging you up.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Motorcraft CM-4433-A = Ford part # E5PZ-9838-B
This is the choke housing I had on my 4180 and it had index marks.
That is an '85 P/N so I don't know...
The engineering number on the part will be different.
This is the choke housing I had on my 4180 and it had index marks.
That is an '85 P/N so I don't know...
The engineering number on the part will be different.
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
FYI here's a shot showing the tabs and slots on the anti-tamper 4180 choke spring housing.
IMO the tab to remove is the one that fits into the big black choke spring housing and NOT the one that keeps the slot in the orange cover in alignment with the lever arm...
IMO the tab to remove is the one that fits into the big black choke spring housing and NOT the one that keeps the slot in the orange cover in alignment with the lever arm...
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