My 1987 Mustang LX 2.3 will crank up & run idle all day but goes dead in drive..

Hello, What happens if you put it in drive and try to accelerate before it dies? Also, there are a lot of issues that come from storing a vehicle for 15 years. Deterioration of many rubber and plastic components is only the beginning, and corrosion of metal parts is almost guaranteed. Unless the garage was temperature controlled, there is a high chance that you will need to put in some extra work on the vehicle. All of the vacuum lines should be replaced one by one. The distributor and distributor rotor should be inspected and cleaned or replaced. The fuel should be drained and replaced, and the fuel filter should be replaced as well. All fluids and filters should be changed: engine oil, transmission fluid, coolant, differential, power steering, air filter Once these maintenance items are done, a complete inspection of the vehicle should be done as well. If you have issues after completing all maintenance, begin diagnosing vacuum leaks first by spraying a mist of air around the engine until you find a place that causes the engine speed and sound to change. There is likely a vacuum leak at that location.