Diagnostic Aids
WARNING: This page is about a different car, the 2003 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
Performing fuel injector coil test may help isolate an intermittent condition. See FUEL INJECTOR COIL TEST under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4.0L AURORA article. If an intermittent condition is suspect, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.