2.3L Trouble Starting when cold

I have an 86 mustang with the standard 2.3L engine with 120,000 miles. When the car is cold, like in the mornings, it will start but will immediately shut off. I can see the tach rev up to 1500rpm and drop until it shuts off. I have to keepit running with the accelerator for about 5 minutes until it warms up and will run on its own. Help