Hard to start when cold, starts fine when warmed up

Sorry, been quite a while since I contacted you. Lot has happened. Did finally get around to replacing the "coolant temperature" sensor. Seems to have corrected the problem. Will not know for sure until winter gets closer. Going to need quite a bit of body work.

Well I am back. Cold weather is upon us and the hard start problem is coming back. So far I have replaced the following: Fuel pump, fuel pressure switch, complete throttle body and engine coolant temp sensor. No starting problems in the warmer weather. First cold weather then the problem came back. Truck listed above is a XLT Lariat.

The problem only occurs in cold weather. Once started the engine will restart easily. I have less than 132,000 miles on the truck. I pull my car hauler and camper with no problem. So I have plenty of power. If I had a loss of compression I would be able to tell. One thing it does do is when at idle the engine will go from 750 RPM's to about 1,500 RPM's then back down. Does it multiple times, even when the engine is warmed up.

Since there is 3 hours time difference I will do this tomorrow. Will clean, reinstall and let you know tomorrow.

Clarification, when I looked at the time stamp it shows 3 hours difference. I am in southern Ohio so our time is the same. I replaced the MAF's module. Seems to be idling fine but was still hard to start. Might be because I tried to start it right after instillation. Cannot remember where I read it but one article said if replacing the MAF's that the computer would have to readjust (recalibrate) itself and I did not give it time to do so. Supposed to be cooler overnight so will test it again on Friday morning. After warming up it had restarted with no problems and the idling seemed smother but the jury is still out on that also. Time will tell. Could I possibly have a "Crankshaft Position Sensor" that is breaking down in cold weather? As I mentioned it starts fine when the engine is warm and in warmer weather.

Live not far from Portsmouth. As far as the crank sensor I was grasping at straws. I replaced the MAF sensor yesterday. Outside temperature at 9:30 am today 11/13/2020 shows 40 degrees. Truck cranked between 8-10 seconds before it started. When the weather is colder it cranks longer. About ready to take it to the Ford garage. Know it will be expensive but not sure what else to do.

Well it turns out the MAF sensor did not change things a bit. Still hard to start when cold. The engine RPM still surges while at idle. Not sure what else to do. As far as the temperature sensor (coolant temperature sensor) it was replaced but the weather started warming up and the truck had no issues. Now that it has started cooling down. Same old problems. To say I am frustrated would be putting it mildly.

Fuel pressure is a good bit higher than 15PSI. Still having the fluctuation of the engine rpm at idle. Beginning to think it is a computer problem. I have tried so many different things. I have scratched my head, my backside and several spots I will not mention trying to figure out what is wrong with the truck. Next step is the Ford garage.

Well, it has been a long time and a lot of money spent but finally got the darn thing fixed. As a reminder: hard to start in cold weather. When warm weather came around no problem. Changed fuel pump, pressure switch for fuel pump, throttle body and coolant head temperature sensor. Even put a new MAF sensor on it. All to no avail. Took the truck to a specialty shop. $1,127.00 later it is fixed. In the years I had the truck I put a cold air induction system on it. (Went from about a 4" to about a 6" air intake. Also put a little "black box" that was supposed to retune the computer. Well the first mechanic had replaced the fuel pump and removed the black box. Still had the initial problem of hard starting. Turns out that since I had taken the factory air intake system off and put the other on the MAF sensor was not seeing the complete air flow. When the guy took off the black box(giving funky reading on scanner) the truck computer thought I was using E-85 all the time. Cold weather it caused it to flood out. When the specialty shop run the diagnostics on it showed a setting for flex fuel due to the intake that I had put on. He put a stock air system back on it and updated and reset the computer. Problem solved. All because I was getting fancy with some newer stuff. Have learned to leave well enough alone. With all the garage bills it cost almost $2,400.00. Good thing is that it runs great now. One other thing I learned. On some F-150 in the 2010 year range Ford had a problem with the flex fuel system. They also had a small problem with what turned out to be a vacuum leak. Back of block and the only way to find it was to spray carburetor cleaner which cause the RPMs to change. Bear to fix but still simple. Hope my bad experience helps out someone else.

My fault for not putting that into the notes that I had sent. The truck had run great for years. I think the problem got compounded when the original mechanic changed the fuel pump and took off the black box. It may have cured the original problem but allowed another problem to develop that showed the same symptoms. The black box corrected the original air flow setting. May have had a fuel pump going bad. When fuel pump changed and the black box removed the computer saw it as E-85. Warm weather no problem but in cold weather, that was a different story. Just glad it is fixed.