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Engine is running rough out of nowhere?!

bbbc3

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My truck has been running perfectly until I drove it to the airport and was gone 11 days. When I got back it was very hard to start and would not idle without dying. It feels like it is miss firing. Going down the road at a steady rpm it seems like it runs fine. It is very choppy. I adjusted the mixer screws on the carb and that stopped it from dying at idle but it’s still running really rough.
Any thoughts?
 


RonD

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Water in the gas tank, maybe, the sitting for a few days made this come to mind

All gasoline has some water in it, comes from condensation is the storage tanks
Too much water is called "bad gas"

Gasoline and water can not mix/bond together
Water is heavier than gasoline
Normally as the fuel sloshes around when driving it stays mixed enough to not get too much water being sucked in all at once
When vehicle sits for a week or so the water will settle to the bottom of the tank
Fuel is sucked from the bottom of the tank........................
Same happens in the carb, water settles to bottom of float bowl

Ethanol can bond with water, which is why its used as an additive in winter fuel, to prevent water from freezing in fuel lines or gas tank

You can add Boost or HEET, ethanol additives, to allow any water to pass thru the system/engine without any issues


May not be your issue at all, just your comment on vehicle sitting for 11 days reminded me of this
 

bbbc3

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@RonD this sounds plausible. I just topped my truck off with non-ethanol fuel before my trip. I’ll give her a try and report back to this thread.
 

4x4prepper

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google: why is ethanol added for winter gas

> which is why its used as an additive in winter fuel,

The Vapor Rub: Summer versus Winter Gasoline Explained

https://www.caranddriver.com/news/a15339380/the-vapor-rub-summer-versus-winter-gasoline-explained/

They use it because it is cheap and to promote winners and losers in the farming market that favors big agr tied to powerful (paid for) politicians.

Read This Before You Fuel Up This Winter

https://smarterfuelfuture.org/blog/details/read-this-before-you-fuel-up-this-winter/

"Unexpected water issues in your engines such as gum formation and engine corrosion could be the result of higher levels of ethanol being blended into fuel due to the Renewable Fuel Standard. "

> When I got back it was very hard to start and would not idle without dying. It feels like it is miss firing.

From working on vehicles left at air port parking lots, that needed to be towed for starting issues, here is what I have observed and figured out. The vehicles are vandalized to get back at people with larger gas vehicles (stuff put in the gas tank) or to promote the repair business associated with the local tow company (the vehicle I am citing).

I had one customer ask me nicely to look at her boyfriend's GM truck, even though they know I only like to work on Ford trucks. I found two disconnected injector harnesses on one side and three disconnected plug wires on the other (right) side of the V-8. They disconnected what could not be easily seen by opening the hood. I reconnected everything and it ran fine. Which is subjective since it probably had the leaking upper manifold with no filler neck, but, I was not about to open that can of worms on something I did not want to work on. Then I found a work around for his long standing problem of GM's wonderful sliding sunroof getting stuck in the open position.

I would suspect your vehicle was vandalized. It is very easy to remove a locking gas cap or get into a early Ford and pop the hood without being noticed. On many B2/Rangers you can disconnect the plug wires just by reaching in from the wheel well. Instead of chasing carb problems, I would look at what someone could have done to the vehicle or swap out the TFI module if you still are using one.

I now fill my vehicles and small equipment with non-ethanol gas whenever possible. I encouraged my neighbor to do the same with his 2018 Expo and 3.5L twin turbo, he said it drove completely different and was much better doing his long haul at 80+ MPH to FL from GA.
 

bbbc3

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@4x4prepper thats an interesting theory and thanks for sharing. I highly doubt that someone would vandalize my truck to prove a point. Also the issue was immediate when starting the truck. Anything put in my gas tank would take a few minutes for symptoms to appear. I only run non-ethanol fuel too. I have a spare TFI module so I can try that but my experience with those is that when they are bad the truck does start at all.

We’ll figure it out.
 

bbbc3

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*Update - I replaced the fuel filter and that seems to have fixed my issue.
I didn’t think it would be fuel filter related because it drove fine at higher RPMs. I guess something was blocking fuel flow at lower fuel pressure and the mechanical pump must have worked around it at higher pressure.
:icon_confused: This truck never misses an opportunity to stump me.
 

4x4prepper

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The fuel pump puts out more volume at higher RPMs, the increase in pressure is minimal on most Ford carb engines at higher RPMs. If water or piss is introduced into the gas tank, a good filter (aka Motorcraft) on an EFI vehicle will collect water, on the carb the fine mesh filter collects the water sludge probably because it has rust in it. Just an observation from taking filters apart.

I run a clear glass filter before the carb filter for this reason, to see what is going on, plus, the much better filter. Glad to hear it was a <$10 fix.
 

bbbc3

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*another update - seems that it was the power valve in the carb. I had to pull the carb when replacing the intake manifold gasket and while I was there I replaced the power valve and that seems to have taken care of the issue.
 

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