Stalls/Quits, Hesitation/Stumble

Ensure base idle speed is correct. See ADJUSTMENTS - 3.0L article.
Check idle air control systems. See appropriate SYSTEM/COMPONENT TESTS article.
Check ignition system. See BASIC TESTING - 3.0L article.
Check fuel delivery system. See SYSTEM/COMPONENT TESTS article.
Check EGR system. See SYSTEM/COMPONENT TESTS article.
Check engine compression and mechanical condition.
Check exhaust system for leaks or restrictions.