My car won't start in very cold weather! What's wrong with it and what's the solution?

I've got a Ford Taurus 2003. When it gets very cold about 0°C = 32°F, it cranks but won't start. There is no problem with the battery and the cables are tightened and fixed. However when I open the fuse box and move the fuses up and down and push them down real hard it starts just as normal. Any ideas?

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