Preliminary Inspection

• Verify on-vehicle diagnostics are working by performing DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.0L AURORA article.
• Ensure Powertrain Control Module (PCM) and Malfunction Indicator Light (MIL) are functioning properly.
• Ensure there are no DTCs stored, or only intermittent DTCs are present.
• Ensure the Engine Coolant Temperature (ECT) is not above 266°F (130°C). This will cause the PCM to operate in the Engine Metal Overtemp Mode. While in this state, the PCM will turn OFF four cylinders at a time to prevent the engine coolant temperature from reaching damaging levels. Engine Metal Overtemp can be perceived as a lack of power, engine miss, or rough idle. If the engine is operating in the Engine Metal Overtemp mode, go to DTC P1258: OVER TEMPERATURE CONDITION under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.0L AURORA article.
• Scan tool data is within the normal operating range. See PIN VOLTAGE CHARTS - AURORA article.
• Ensure PCM grounds are clean, tight, and properly located.
• Check vacuum hoses for splits, kinks, leaks, restrictions and proper connections. Ensure vacuum hoses are correctly routed as shown on vehicle emission control information label.
• Intake air system for a dirty or damaged air cleaner element or housing, any damaged or collapsed intake air ducts or any poor intake air system connections.
• Air leaks at the throttle body and/or intake manifold.
• Check ignition wires for cracking, hardness, proper routing and carbon tracking.
• Check wiring for proper connections and routing, pinches, burns, cuts or other damage.
• Engine cooling system leaks.
• Ensure fuel control system is operating properly. See FUEL SYSTEM CHECKS in BASIC DIAGNOSTIC PROCEDURES - 4.0L AURORA article.
• Perform fuel system pressure test. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEM CHECKS in BASIC DIAGNOSTIC PROCEDURES - 4.0L AURORA article.
• Perform a careful visual inspection of all systems.

After all checks have been performed, verify customer complaint and locate correct symptom. Check items indicated under that symptom. These procedures will normally recommend testing of a specific system or component, such as EGR, ignition, TCC, etc. See SYSTEM & COMPONENT TESTING - 4.0L AURORA article for test procedures.