That code (referencing the coolant temperature sensor) would be a good place to start. If you have a scanner, see what that ECT sensor is reading. It should report ambient temperature when cold and near the thermostat setpoint when warmed up.
If it’s flaky, and reporting a strange number, it will cause the computer to mess up fuel delivery and cause hard hot starts. A workaround is to hold the gas down while cranking. This temporarily stops injector flow and is the “clear flood” mode.
Here are the diagnostics for P0118 on a 1998 350. No guarantee that it is applicable to the 4.3, but maybe it will help.
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach