My 98 f-150 4.6 will only start on cold days if I hold the gas pedal down a little. It just recently started this and I noticed it when I used the command start one cold morning, it turned over but wouldn't fire. When I tried starting with the key it would only fire after giving it some gas. It's getting worse as this morning I had to rev it for a couple minutes before it would idle without stalling. Once it warms up it seems fine and will start easily all day. Anyone else have this problem? Thanks in advance and Happy New Year!