I have seen numerous posts for this, but haven't been able to find one that had a solution.
My 2004 Ranger with the 4.0L and 5speed stick starts bucking and jerking in cold weather, but the worst is when it snows. I thought it may be the coil pack having issues when it was damp, but it's ok in the rain as long as the temperature is warm. I read that it could be the camshaft synchronizer, but I'm told that the 4.0L SOHC doesn't have one.
It looks like a lot of owners are having this problem; has anyone found a fix yet?

 

Is there any differences when engine is cold and after warm up?
i.e. does it run OK in snowy weather just after starting(cold start) and then start to run poor only after it warms up

The air fuel mix used in any engine is based of the WEIGHT of the air and the WEIGHT of the fuel
Gasoline engines use 14.7:1 ratio, so..........
14.7 POUNDS of air is mixed with 1 POUND of gasoline
or
14.7 grams of air is mixed with 1 gram of gasoline

This is why the 200mpg carburetor was never possible, and why "pre-vaporizers" are a bunch of Whooey, lol, laws of physics suck sometimes.

The weight of the gasoline doesn't change much with temperature
But the weight of the air DOES CHANGE with temperature.

"Hot air rises".........most have heard that, and if you have ever seen a hot air balloon fly then you can believe it as well, lol.

Why does hot air rise?
Simple, because it is lighter than cold air, as air is warmed up the molecules get farther apart so there are less and it "floats" on denser colder air, balloon goes up.

Air also gets "thinner" as you go up in elevation, not as dense, so weighs less

When you want to get a good 14.7:1 air:fuel mix you need to know the air temperature so you can calculate how much the air weighs so you know how much gasoline to add.
You also need to know the air density to compensate for elevation.

Fuel injected engines all have an IAT(intake air temp) sensor, and a MAP(manifold air pressure) or a MAF(Mass Air Flow) sensor, for the above reasons.

MAF sensors serve two purposes, Ford uses a "heated wire" MAF, as air is pulled into the engine, it cools down this heated wire, the amount of cooling tells air temp to a point, but air density is what it's main purpose is for, "thicker air" cools wire faster.
IAT sensor was usually found on the upper intake of most engines.
But in 1995 Ford added it to MAF sensor setup, MAF sensor changed from 4 wire to 6 wire harness, outside 2 wires are for the IAT sensor.

So for your 2004 I would clean the MAF/IAT sensor and see if that helps with cold weather running.


A good investment is a Bluetooth OBDII reader, under $50.
They work on ANY vehicle sold in the US/Canada since 1996, it's the Law.

These use your smartphone or tablet(with Bluetooth) to display information from the computer, like codes, but also REAL TIME data while engine and sensors are working.
So you can SEE the air temp the computer is seeing from the sensors
Also engine coolant temp can be viewed in real time, if an engine is running too cold for too long it will start to run poorly, needs to get up to operating temp, 190degF, as soon as possible.

If you get a Bluetooth reader get a short extension cable with it, $5-$8, some vehicles OBDII plugs are recessed and this cable makes it easier to plugin the reader, this works with ANY vehicle, not a Ford thing, not GM thing, Toyota, Nissan, Audi all had to use this after 1996 or couldn't be sold here

 

It doesn't matter what the engine temperature is, it has done it when it's cold and after warming up. I don't recall it happening ONLY with cold, there has to be moisture in the air, but especially when it's snowing for some reason.