2005 F150
4.6 Liter V845,000 miles
A few weeks ago my '05 F150 started acting up. I took it to Auto Zone and a Mechanic numerous times and it does not show any errors.

I believe I have deduced that it acts up when the weather goes below 35 (Michigan). It runs perfectly fine when it's in the 40's but then when it gets cold outside it starts it's shenanigans.

At idle it will jump rpm's, kick, stumbles, jump, etc then when I press the gas it has absolutely no get up n go. I can "floor it" and it does nothing.
​​​​ This will happen if I have been driving for 5min or 50min. Last week and early this week we had 40⁰-60⁰. No issues. Then it went below 35⁰ and it's all back again. To the point where it feels like it's going to die.

I thought I bought bad fuel so I used fuel injector a few times now. Had Fuel Filter Changed. Air Filter is new. Regular Maintenance is up to date. Replaced a bad ignition coil last year. Replace the Fuel Relay Module (I think that's what it's called. It's under the rear of the truck) last year.

Not sure where to start...O2 sensor? Coils? Spark Plugs? Help please! We try to do as many repairs as we can on our own.

 

Anyone???

 

Try some "gas line antifreeze"...while I'm not certain of the ingredients I'm pretty sure it's just alcohol...burns excess water out of your gas if you have any in there.

When I was stationed in New York, it was common practice to use it at the beginning of the cold season because the change in weather often caused a lot of moisture buildup in the tank, especially if it's a sudden cold snap or your local gas station secretly waters down the gas. You can also always do the Scotty kilmer gallon of lacquer thinner in half a tank...that'll clean out your cats while it's burning off the water...

You say starting issues...if you got the cheapest battery and a marginal alternator, it might not have enough cca (COLD cranking amps) to start when the temp drops. Most people don't pay attention to that when they buy the battery but if you live in a colder area, such as you do, you'll want your battery to have some extra juice when it's cold out.

Other issues include condensation and water getting in places you don't want it, such as your plug wires. Dielectric grease should be used to help prevent issues on critical electrical components such as these. When you changed the coil, did you change both (or all 6/8 if you have coil on plug)? Best to replace all/both coils at the same time for consistency.

These are a few cheapie fixes you might entertain before getting crazy and throwing parts at it. Good luck.

Also, not sure how similar your 4.6 is to mine in my 98, but they're notorious for carbon builup in the intake tract and it's peripheral sensors. Pulling it apart and deep cleaning never hurts.