1994 Skylark Custom

1994 Buick Skylark Custom. Mileage: 100,000 Quad 4 3.3L. My Car won't start when it's cold outside. If it's below 50F, the engine will turn over and crank, but nothing will fire. I recently replaced both the ignition coil and coil cover. If I let the car sit in the daylight all day, it will start fine, but any time it is cold out, it won't start at all. I've checked the battery, which is fine. My entire family and three mechanics are out of suggestions. Please Help!