no twin15

1992 mustang LX coup, 5.0 with 5 speed manual trans, 273k. Car is basically stock. Has Mac exhaust with NO cats. The problem is when the ambient air is 70* or colder the engine shuts off, whether the engine is cold or at operating temp. It will do it anytime, even on the interstate, very embarrassing especially when it backfires. Also the engine doesn't race when cold (only for 1 min). When engine is at operating temperture it races around 1500 down to 1000 after two min or so. What i did so far is Replaced throttle position valve, vehicle speed sensor, cleaned salt and pepper shakers and used Dielectric silicone compound. Runs fine in warmer temperature. Any help will be greatly appreciated. Thanks John