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[osconda]

Here's the history.

I live in Central Texas. Truck would start fine when the days were warm (March - October). Once it starts getting colder (i.e. 55 degr or less) and the truck has been sitting all night, it will take several cranks (3 or more) for it to start. But it would finally start and run real rough and would keep running.

In '06 I was going hunting in Colorado and knew the temps would be pretty cold in the mountains so I heard that it might be easier to start if I had the latest Ford engine program installed. I took it to dealership and had the latest program installed. The truck did not start any easier after that, but it no longer ran real rough when it started. It seemed to have more power while it was cold. It probably around 20 degrees in the mountains and the truck would not start. Got a generator fired up and plugged in the engine block heater and a battery charger and let that simmer a while. About 30 min. later I was able to start the truck on the 2nd crank. This situation happened about 2 years ago and I've been dealing with it since then.

This year in July I went back to Colorado to do some prescouting. After it had been sitting for a few days I tried to start it. The temp was about 70 degrees. I cranked it maybe 5 times before it finally started. The truck was at around 10,000 ft. elevation. If I would have been in Texas and it was 70 degrees it would have fired right up.

So it seems like I have two different issues and one might be masking the other. There has to be something related to barometric pressure (i.e. elevation) or the truck should have started right away since it wasn't cold in Colorado. In Texas though, where I'm only at around 700 ft. elevation, cold seems to be the problem. So I guess in Colorado when it's cold, both issues are working against me.

I recently replaced the starter, both batteries, and alternator. So all that stuff is tiptop. Any ideas on what's causing these starting issues? What kind of sensors should I be checking?

Thanks for your help.