95 Trooper - engine quits after warm up

The engine starts up fine and maintains an idle of about 1200-1300 rpm. Once
the engine is warm after about 4 minutes the idle is supposed to come down
to about 800-900 rpm. Instead the engine quits. If I push the gas, the
engine will struggle to stay running but once I remove my foot from the gas,
the engine quits. Following this the engine cannot be restarted unless many
hours have passed and the engine has to warm up again. The engine was
recently replaced along with a Starter Relay Switch. Any help would be
appreciated.