I have owned my 99' 4.0 ranger for a year now and continue to have a problem with the truck starting hard when the outside temp drops up here in te north.
I was also looseing coolant as well. When its cold out and I start the truck it will crank for a few seconds and when it starts it idles very rough for 10 to 20 seconds and then idles fine. when it is below 30 it usally starts rough and stalls out, usally on restart its fine. My mechanic replaced the lower intake and that cured the coolant leak. He said the hard start was the the plugs so he changed them and that seemed to help for a while, but the rough start came back when cold and eventually set a cel ( misfire on #4 ) He changed the plugs again and it helped for a while but it returned again and Cel with a misfire again. He has checked all the sensors, fuel pressure, coil packs, ect. I heard it could be the upper intake gaskets leaking when cold and after it runs a few seaond they swell and are fine. Maybe the new lower intake is leaking air but not leaking the coolant agin.

thanks,
mike