Cranks Normally But Difficult To Start

Check ECM ground and power circuits. See COMPUTERIZED ENGINE CONTROLS in SYSTEM/COMPONENT TESTS article.
Check intake manifold vacuum. Vacuum should be more than 17.7 Hg at idle.
Check air filter element.
Ensure fuel system pressure is correct.
Check Idle Speed Control (ISC) solenoid valve. See SYSTEM/COMPONENT TESTS article.
Check ignition timing.
Check engine compression.