Why won't car run unless warmed up first?

There could be several reasons for this. 1. Bad Fuel (If this is the case, gas mileage should drop significantly) 2. Faulty Sensor 3. Frozen Fuel Line 4. Condensation in the tank 5. Just too cold ...or it could be thousands of other things I had this same problem with my Chevrolet Cheyenne Pickup. It just needed different fuel. Try putting some anti-freeze gas treatment in the tank. You can find it at the gas station when you fill up.